mosquitto.h

Summary
mosquitto.h
Threadslibmosquitto provides thread safe operation, with the exception of mosquitto_lib_init which is not thread safe.
Library version, init, and cleanup
Functions
mosquitto_lib_versionCan be used to obtain version information for the mosquitto library.
mosquitto_lib_initMust be called before any other mosquitto functions.
mosquitto_lib_cleanupCall to free resources associated with the library.
Client creation, destruction, and reinitialisation
Functions
mosquitto_newCreate a new mosquitto client instance.
mosquitto_destroyUse to free memory associated with a mosquitto client instance.
mosquitto_reinitialiseThis function allows an existing mosquitto client to be reused.
Will
Functions
mosquitto_will_setConfigure will information for a mosquitto instance.
mosquitto_will_set_v5Configure will information for a mosquitto instance, with attached properties.
mosquitto_will_clearRemove a previously configured will.
Username and password
Functions
mosquitto_username_pw_setConfigure username and password for a mosquitto instance.
Connecting, reconnecting, disconnecting
Functions
mosquitto_connectConnect to an MQTT broker.
mosquitto_connect_bindConnect to an MQTT broker.
mosquitto_connect_bind_v5Connect to an MQTT broker.
mosquitto_connect_asyncConnect to an MQTT broker.
mosquitto_connect_bind_asyncConnect to an MQTT broker.
mosquitto_connect_srvConnect to an MQTT broker.
mosquitto_reconnectReconnect to a broker.
mosquitto_reconnect_asyncReconnect to a broker.
mosquitto_disconnectDisconnect from the broker.
mosquitto_disconnect_v5Disconnect from the broker, with attached MQTT properties.
Publishing, subscribing, unsubscribing
Functions
mosquitto_publishPublish a message on a given topic.
mosquitto_publish_v5Publish a message on a given topic, with attached MQTT properties.
mosquitto_subscribeSubscribe to a topic.
mosquitto_subscribe_v5Subscribe to a topic, with attached MQTT properties.
mosquitto_subscribe_multipleSubscribe to multiple topics.
mosquitto_unsubscribeUnsubscribe from a topic.
mosquitto_unsubscribe_v5Unsubscribe from a topic, with attached MQTT properties.
mosquitto_unsubscribe_multipleUnsubscribe from multiple topics.
Struct mosquitto_message helper functions
Functions
mosquitto_message_copyCopy the contents of a mosquitto message to another message.
mosquitto_message_freeCompletely free a mosquitto_message struct.
mosquitto_message_free_contentsFree a mosquitto_message struct contents, leaving the struct unaffected.
Network loop (managed by libmosquitto)The internal network loop must be called at a regular interval.
Functions
mosquitto_loop_foreverThis function call loop() for you in an infinite blocking loop.
mosquitto_loop_startThis is part of the threaded client interface.
mosquitto_loop_stopThis is part of the threaded client interface.
mosquitto_loopThe main network loop for the client.
Network loop (for use in other event loops)
Functions
mosquitto_loop_readCarry out network read operations.
mosquitto_loop_writeCarry out network write operations.
mosquitto_loop_miscCarry out miscellaneous operations required as part of the network loop.
Network loop (helper functions)
Functions
mosquitto_socketReturn the socket handle for a mosquitto instance.
mosquitto_want_writeReturns true if there is data ready to be written on the socket.
mosquitto_threaded_setUsed to tell the library that your application is using threads, but not using mosquitto_loop_start.
Client options
Functions
mosquitto_opts_setUsed to set options for the client.
mosquitto_int_optionUsed to set integer options for the client.
mosquitto_void_optionUsed to set void* options for the client.
mosquitto_reconnect_delay_setControl the behaviour of the client when it has unexpectedly disconnected in mosquitto_loop_forever or after mosquitto_loop_start.
mosquitto_max_inflight_messages_setThis function is deprected.
mosquitto_message_retry_setThis function now has no effect.
mosquitto_user_data_setWhen mosquitto_new is called, the pointer given as the “obj” parameter will be passed to the callbacks as user data.
mosquitto_userdataRetrieve the “userdata” variable for a mosquitto client.
TLS support
Functions
mosquitto_tls_setConfigure the client for certificate based SSL/TLS support.
mosquitto_tls_insecure_setConfigure verification of the server hostname in the server certificate.
mosquitto_tls_opts_setSet advanced SSL/TLS options.
mosquitto_tls_psk_setConfigure the client for pre-shared-key based TLS support.
Callbacks
Functions
mosquitto_connect_callback_setSet the connect callback.
mosquitto_connect_with_flags_callback_setSet the connect callback.
mosquitto_connect_v5_callback_setSet the connect callback.
mosquitto_disconnect_callback_setSet the disconnect callback.
mosquitto_disconnect_v5_callback_setSet the disconnect callback.
mosquitto_publish_callback_setSet the publish callback.
mosquitto_publish_v5_callback_setSet the publish callback.
mosquitto_message_callback_setSet the message callback.
mosquitto_message_v5_callback_setSet the message callback.
mosquitto_subscribe_callback_setSet the subscribe callback.
mosquitto_subscribe_v5_callback_setSet the subscribe callback.
mosquitto_unsubscribe_callback_setSet the unsubscribe callback.
mosquitto_unsubscribe_v5_callback_setSet the unsubscribe callback.
mosquitto_log_callback_setSet the logging callback.
mosquitto_string_optionUsed to set const char* options for the client.
mosquitto_reconnect_delay_setControl the behaviour of the client when it has unexpectedly disconnected in mosquitto_loop_forever or after mosquitto_loop_start.
SOCKS5 proxy functions
Functions
mosquitto_socks5_setConfigure the client to use a SOCKS5 proxy when connecting.
Utility functions
Functions
mosquitto_strerrorCall to obtain a const string description of a mosquitto error number.
mosquitto_connack_stringCall to obtain a const string description of an MQTT connection result.
mosquitto_reason_stringCall to obtain a const string description of an MQTT reason code.
mosquitto_string_to_commandTake a string input representing an MQTT command and convert it to the libmosquitto integer representation.
mosquitto_sub_topic_tokeniseTokenise a topic or subscription string into an array of strings representing the topic hierarchy.
mosquitto_sub_topic_tokens_freeFree memory that was allocated in mosquitto_sub_topic_tokenise.
mosquitto_topic_matches_subCheck whether a topic matches a subscription.
mosquitto_topic_matches_sub2Check whether a topic matches a subscription.
mosquitto_pub_topic_checkCheck whether a topic to be used for publishing is valid.
mosquitto_pub_topic_check2Check whether a topic to be used for publishing is valid.
mosquitto_sub_topic_checkCheck whether a topic to be used for subscribing is valid.
mosquitto_sub_topic_check2Check whether a topic to be used for subscribing is valid.
mosquitto_validate_utf8Helper function to validate whether a UTF-8 string is valid, according to the UTF-8 spec and the MQTT additions.
One line client helper functions
Functions
mosquitto_subscribe_simpleHelper function to make subscribing to a topic and retrieving some messages very straightforward.
mosquitto_subscribe_callbackHelper function to make subscribing to a topic and processing some messages very straightforward.
Properties
Functions
mosquitto_property_add_byteAdd a new byte property to a property list.
mosquitto_property_add_int16Add a new int16 property to a property list.
mosquitto_property_add_int32Add a new int32 property to a property list.
mosquitto_property_add_varintAdd a new varint property to a property list.
mosquitto_property_add_binaryAdd a new binary property to a property list.
mosquitto_property_add_stringAdd a new string property to a property list.
mosquitto_property_add_string_pairAdd a new string pair property to a property list.
mosquitto_property_read_byteAttempt to read a byte property matching an identifier, from a property list or single property.
mosquitto_property_read_int16Read an int16 property value from a property.
mosquitto_property_read_int32Read an int32 property value from a property.
mosquitto_property_read_varintRead a varint property value from a property.
mosquitto_property_read_binaryRead a binary property value from a property.
mosquitto_property_read_stringRead a string property value from a property.
mosquitto_property_read_string_pairRead a string pair property value pair from a property.
mosquitto_property_free_allFree all properties from a list of properties.
mosquitto_property_copy_alldest : pointer for new property list src : property list
mosquitto_property_check_commandCheck whether a property identifier is valid for the given command.
mosquitto_property_check_allCheck whether a list of properties are valid for a particular command, whether there are duplicates, and whether the values are valid where possible.
mosquitto_string_to_property_infoParse a property name string and convert to a property identifier and data type.

Threads

libmosquitto provides thread safe operation, with the exception of mosquitto_lib_init which is not thread safe.

If your application uses threads you must use mosquitto_threaded_set to tell the library this is the case, otherwise it makes some optimisations for the single threaded case that may result in unexpected behaviour for the multi threaded case.

Library version, init, and cleanup

Summary
Functions
mosquitto_lib_versionCan be used to obtain version information for the mosquitto library.
mosquitto_lib_initMust be called before any other mosquitto functions.
mosquitto_lib_cleanupCall to free resources associated with the library.

Functions

mosquitto_lib_version

libmosq_EXPORT int mosquitto_lib_version(int *major,
int *minor,
int *revision)

Can be used to obtain version information for the mosquitto library.  This allows the application to compare the library version against the version it was compiled against by using the LIBMOSQUITTO_MAJOR, LIBMOSQUITTO_MINOR and LIBMOSQUITTO_REVISION defines.

Parameters

majoran integer pointer.  If not NULL, the major version of the library will be returned in this variable.
minoran integer pointer.  If not NULL, the minor version of the library will be returned in this variable.
revisionan integer pointer.  If not NULL, the revision of the library will be returned in this variable.

Returns

LIBMOSQUITTO_VERSION_NUMBER, which is a unique number based on the major, minor and revision values.  See Also: mosquitto_lib_cleanup, mosquitto_lib_init

mosquitto_lib_init

libmosq_EXPORT int mosquitto_lib_init(void)

Must be called before any other mosquitto functions.

This function is not thread safe.

Returns

MOSQ_ERR_SUCCESSalways

See Also

mosquitto_lib_cleanup, mosquitto_lib_version

mosquitto_lib_cleanup

libmosq_EXPORT int mosquitto_lib_cleanup(void)

Call to free resources associated with the library.

Returns

MOSQ_ERR_SUCCESSalways

See Also

mosquitto_lib_init, mosquitto_lib_version

Client creation, destruction, and reinitialisation

Summary
Functions
mosquitto_newCreate a new mosquitto client instance.
mosquitto_destroyUse to free memory associated with a mosquitto client instance.
mosquitto_reinitialiseThis function allows an existing mosquitto client to be reused.

Functions

mosquitto_new

libmosq_EXPORT struct mosquitto *mosquitto_new(const char *id,
bool clean_session,
void *obj)

Create a new mosquitto client instance.

Parameters

idString to use as the client id.  If NULL, a random client id will be generated.  If id is NULL, clean_session must be true.
clean_sessionset to true to instruct the broker to clean all messages and subscriptions on disconnect, false to instruct it to keep them.  See the man page mqtt(7) for more details.  Note that a client will never discard its own outgoing messages on disconnect.  Calling mosquitto_connect or mosquitto_reconnect will cause the messages to be resent.  Use mosquitto_reinitialise to reset a client to its original state.  Must be set to true if the id parameter is NULL.
objA user pointer that will be passed as an argument to any callbacks that are specified.

Returns

Pointer to a struct mosquitto on success.  NULL on failure.  Interrogate errno to determine the cause for the failure:

  • ENOMEM on out of memory.
  • EINVAL on invalid input parameters.

See Also

mosquitto_reinitialise, mosquitto_destroy, mosquitto_user_data_set

mosquitto_destroy

libmosq_EXPORT void mosquitto_destroy(struct mosquitto *mosq)

Use to free memory associated with a mosquitto client instance.

Parameters

mosqa struct mosquitto pointer to free.

See Also

mosquitto_new, mosquitto_reinitialise

mosquitto_reinitialise

libmosq_EXPORT int mosquitto_reinitialise(struct mosquitto *mosq,
const char *id,
bool clean_session,
void *obj)

This function allows an existing mosquitto client to be reused.  Call on a mosquitto instance to close any open network connections, free memory and reinitialise the client with the new parameters.  The end result is the same as the output of mosquitto_new.

Parameters

mosqa valid mosquitto instance.
idstring to use as the client id.  If NULL, a random client id will be generated.  If id is NULL, clean_session must be true.
clean_sessionset to true to instruct the broker to clean all messages and subscriptions on disconnect, false to instruct it to keep them.  See the man page mqtt(7) for more details.  Must be set to true if the id parameter is NULL.
objA user pointer that will be passed as an argument to any callbacks that are specified.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

See Also

mosquitto_new, mosquitto_destroy

Will

Summary
Functions
mosquitto_will_setConfigure will information for a mosquitto instance.
mosquitto_will_set_v5Configure will information for a mosquitto instance, with attached properties.
mosquitto_will_clearRemove a previously configured will.

Functions

mosquitto_will_set

libmosq_EXPORT int mosquitto_will_set(struct mosquitto *mosq,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain)

Configure will information for a mosquitto instance.  By default, clients do not have a will.  This must be called before calling mosquitto_connect.

Parameters

mosqa valid mosquitto instance.
topicthe topic on which to publish the will.
payloadlenthe size of the payload (bytes).  Valid values are between 0 and 268,435,455.
payloadpointer to the data to send.  If payloadlen > 0 this must be a valid memory location.
qosinteger value 0, 1 or 2 indicating the Quality of Service to be used for the will.
retainset to true to make the will a retained message.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_PAYLOAD_SIZEif payloadlen is too large.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8.

mosquitto_will_set_v5

libmosq_EXPORT int mosquitto_will_set_v5(struct mosquitto *mosq,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain,
mosquitto_property *properties)

Configure will information for a mosquitto instance, with attached properties.  By default, clients do not have a will.  This must be called before calling mosquitto_connect.

Parameters

mosqa valid mosquitto instance.
topicthe topic on which to publish the will.
payloadlenthe size of the payload (bytes).  Valid values are between 0 and 268,435,455.
payloadpointer to the data to send.  If payloadlen > 0 this must be a valid memory location.
qosinteger value 0, 1 or 2 indicating the Quality of Service to be used for the will.
retainset to true to make the will a retained message.
propertieslist of MQTT 5 properties.  Can be NULL.  On success only, the property list becomes the property of libmosquitto once this function is called and will be freed by the library.  The property list must be freed by the application on error.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_PAYLOAD_SIZEif payloadlen is too large.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8.
MOSQ_ERR_NOT_SUPPORTEDif properties is not NULL and the client is not using MQTT v5
MOSQ_ERR_PROTOCOLif a property is invalid for use with wills.
MOSQ_ERR_DUPLICATE_PROPERTYif a property is duplicated where it is forbidden.

mosquitto_will_clear

libmosq_EXPORT int mosquitto_will_clear(struct mosquitto *mosq)

Remove a previously configured will.  This must be called before calling mosquitto_connect.

Parameters

mosqa valid mosquitto instance.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.

Username and password

Summary
Functions
mosquitto_username_pw_setConfigure username and password for a mosquitto instance.

Functions

mosquitto_username_pw_set

libmosq_EXPORT int mosquitto_username_pw_set(struct mosquitto *mosq,
const char *username,
const char *password)

Configure username and password for a mosquitto instance.  By default, no username or password will be sent.  For v3.1 and v3.1.1 clients, if username is NULL, the password argument is ignored.

This is must be called before calling mosquitto_connect.

Parameters

mosqa valid mosquitto instance.
usernamethe username to send as a string, or NULL to disable authentication.
passwordthe password to send as a string.  Set to NULL when username is valid in order to send just a username.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

Connecting, reconnecting, disconnecting

Summary
Functions
mosquitto_connectConnect to an MQTT broker.
mosquitto_connect_bindConnect to an MQTT broker.
mosquitto_connect_bind_v5Connect to an MQTT broker.
mosquitto_connect_asyncConnect to an MQTT broker.
mosquitto_connect_bind_asyncConnect to an MQTT broker.
mosquitto_connect_srvConnect to an MQTT broker.
mosquitto_reconnectReconnect to a broker.
mosquitto_reconnect_asyncReconnect to a broker.
mosquitto_disconnectDisconnect from the broker.
mosquitto_disconnect_v5Disconnect from the broker, with attached MQTT properties.

Functions

mosquitto_connect

libmosq_EXPORT int mosquitto_connect(struct mosquitto *mosq,
const char *host,
int port,
int keepalive)

Connect to an MQTT broker.

Parameters

mosqa valid mosquitto instance.
hostthe hostname or ip address of the broker to connect to.
portthe network port to connect to.  Usually 1883.
keepalivethe number of seconds after which the broker should send a PING message to the client if no other messages have been exchanged in that time.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_connect_bind, mosquitto_connect_async, mosquitto_reconnect, mosquitto_disconnect, mosquitto_tls_set

mosquitto_connect_bind

libmosq_EXPORT int mosquitto_connect_bind(struct mosquitto *mosq,
const char *host,
int port,
int keepalive,
const char *bind_address)

Connect to an MQTT broker.  This extends the functionality of mosquitto_connect by adding the bind_address parameter.  Use this function if you need to restrict network communication over a particular interface.

Parameters

mosqa valid mosquitto instance.
hostthe hostname or ip address of the broker to connect to.
portthe network port to connect to.  Usually 1883.
keepalivethe number of seconds after which the broker should send a PING message to the client if no other messages have been exchanged in that time.
bind_addressthe hostname or ip address of the local network interface to bind to.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_connect, mosquitto_connect_async, mosquitto_connect_bind_async

mosquitto_connect_bind_v5

libmosq_EXPORT int mosquitto_connect_bind_v5(
   struct mosquitto *mosq,
   const char *host,
   int port,
   int keepalive,
   const char *bind_address,
   const mosquitto_property *properties
)

Connect to an MQTT broker.  This extends the functionality of mosquitto_connect by adding the bind_address parameter and MQTT v5 properties.  Use this function if you need to restrict network communication over a particular interface.

Use e.g.  mosquitto_property_add_string and similar to create a list of properties, then attach them to this publish.  Properties need freeing with mosquitto_property_free_all.

Parameters

mosqa valid mosquitto instance.
hostthe hostname or ip address of the broker to connect to.
portthe network port to connect to.  Usually 1883.
keepalivethe number of seconds after which the broker should send a PING message to the client if no other messages have been exchanged in that time.
bind_addressthe hostname or ip address of the local network interface to bind to.
propertiesthe MQTT 5 properties for the connect (not for the Will).

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.
MOSQ_ERR_DUPLICATE_PROPERTYif a property is duplicated where it is forbidden.
MOSQ_ERR_PROTOCOLif any property is invalid for use with CONNECT.

See Also

mosquitto_connect, mosquitto_connect_async, mosquitto_connect_bind_async

mosquitto_connect_async

libmosq_EXPORT int mosquitto_connect_async(struct mosquitto *mosq,
const char *host,
int port,
int keepalive)

Connect to an MQTT broker.  This is a non-blocking call.  If you use mosquitto_connect_async your client must use the threaded interface mosquitto_loop_start.  If you need to use mosquitto_loop, you must use mosquitto_connect to connect the client.

May be called before or after mosquitto_loop_start.

Parameters

mosqa valid mosquitto instance.
hostthe hostname or ip address of the broker to connect to.
portthe network port to connect to.  Usually 1883.
keepalivethe number of seconds after which the broker should send a PING message to the client if no other messages have been exchanged in that time.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_connect_bind_async, mosquitto_connect, mosquitto_reconnect, mosquitto_disconnect, mosquitto_tls_set

mosquitto_connect_bind_async

libmosq_EXPORT int mosquitto_connect_bind_async(struct mosquitto *mosq,
const char *host,
int port,
int keepalive,
const char *bind_address)

Connect to an MQTT broker.  This is a non-blocking call.  If you use mosquitto_connect_bind_async your client must use the threaded interface mosquitto_loop_start.  If you need to use mosquitto_loop, you must use mosquitto_connect to connect the client.

This extends the functionality of mosquitto_connect_async by adding the bind_address parameter.  Use this function if you need to restrict network communication over a particular interface.

May be called before or after mosquitto_loop_start.

Parameters

mosqa valid mosquitto instance.
hostthe hostname or ip address of the broker to connect to.
portthe network port to connect to.  Usually 1883.
keepalivethe number of seconds after which the broker should send a PING message to the client if no other messages have been exchanged in that time.
bind_addressthe hostname or ip address of the local network interface to bind to.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_connect_async, mosquitto_connect, mosquitto_connect_bind

mosquitto_connect_srv

libmosq_EXPORT int mosquitto_connect_srv(struct mosquitto *mosq,
const char *host,
int keepalive,
const char *bind_address)

Connect to an MQTT broker.  This is a non-blocking call.  If you use mosquitto_connect_async your client must use the threaded interface mosquitto_loop_start.  If you need to use mosquitto_loop, you must use mosquitto_connect to connect the client.

This extends the functionality of mosquitto_connect_async by adding the bind_address parameter.  Use this function if you need to restrict network communication over a particular interface.

May be called before or after mosquitto_loop_start.

Parameters

mosqa valid mosquitto instance.
hostthe hostname or ip address of the broker to connect to.
keepalivethe number of seconds after which the broker should send a PING message to the client if no other messages have been exchanged in that time.
bind_addressthe hostname or ip address of the local network interface to bind to.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_connect_async, mosquitto_connect, mosquitto_connect_bind

mosquitto_reconnect

libmosq_EXPORT int mosquitto_reconnect(struct mosquitto *mosq)

Reconnect to a broker.

This function provides an easy way of reconnecting to a broker after a connection has been lost.  It uses the values that were provided in the mosquitto_connect call.  It must not be called before mosquitto_connect.

Parameters

mosqa valid mosquitto instance.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_connect, mosquitto_disconnect, mosquitto_reconnect_async

mosquitto_reconnect_async

libmosq_EXPORT int mosquitto_reconnect_async(struct mosquitto *mosq)

Reconnect to a broker.  Non blocking version of mosquitto_reconnect.

This function provides an easy way of reconnecting to a broker after a connection has been lost.  It uses the values that were provided in the mosquitto_connect or mosquitto_connect_async calls.  It must not be called before mosquitto_connect.

Parameters

mosqa valid mosquitto instance.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_connect, mosquitto_disconnect

mosquitto_disconnect

libmosq_EXPORT int mosquitto_disconnect(struct mosquitto *mosq)

Disconnect from the broker.

Parameters

mosqa valid mosquitto instance.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.

mosquitto_disconnect_v5

libmosq_EXPORT int mosquitto_disconnect_v5(
   struct mosquitto *mosq,
   int reason_code,
   const mosquitto_property *properties
)

Disconnect from the broker, with attached MQTT properties.

Use e.g.  mosquitto_property_add_string and similar to create a list of properties, then attach them to this publish.  Properties need freeing with mosquitto_property_free_all.

Parameters

mosqa valid mosquitto instance.
reason_codethe disconnect reason code.
propertiesa valid mosquitto_property list, or NULL.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_DUPLICATE_PROPERTYif a property is duplicated where it is forbidden.
MOSQ_ERR_PROTOCOLif any property is invalid for use with DISCONNECT.

Publishing, subscribing, unsubscribing

Summary
Functions
mosquitto_publishPublish a message on a given topic.
mosquitto_publish_v5Publish a message on a given topic, with attached MQTT properties.
mosquitto_subscribeSubscribe to a topic.
mosquitto_subscribe_v5Subscribe to a topic, with attached MQTT properties.
mosquitto_subscribe_multipleSubscribe to multiple topics.
mosquitto_unsubscribeUnsubscribe from a topic.
mosquitto_unsubscribe_v5Unsubscribe from a topic, with attached MQTT properties.
mosquitto_unsubscribe_multipleUnsubscribe from multiple topics.

Functions

mosquitto_publish

libmosq_EXPORT int mosquitto_publish(struct mosquitto *mosq,
int *mid,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain)

Publish a message on a given topic.

Parameters

mosqa valid mosquitto instance.
midpointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the publish callback to determine when the message has been sent.  Note that although the MQTT protocol doesn’t use message ids for messages with QoS=0, libmosquitto assigns them message ids so they can be tracked with this parameter.
topicnull terminated string of the topic to publish to.
payloadlenthe size of the payload (bytes).  Valid values are between 0 and 268,435,455.
payloadpointer to the data to send.  If payloadlen > 0 this must be a valid memory location.
qosinteger value 0, 1 or 2 indicating the Quality of Service to be used for the message.
retainset to true to make the message retained.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_PROTOCOLif there is a protocol error communicating with the broker.
MOSQ_ERR_PAYLOAD_SIZEif payloadlen is too large.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8
MOSQ_ERR_QOS_NOT_SUPPORTEDif the QoS is greater than that supported by the broker.
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

See Also

mosquitto_max_inflight_messages_set

mosquitto_publish_v5

libmosq_EXPORT int mosquitto_publish_v5(struct mosquitto *mosq,
int *mid,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain,
const mosquitto_property *properties)

Publish a message on a given topic, with attached MQTT properties.

Use e.g.  mosquitto_property_add_string and similar to create a list of properties, then attach them to this publish.  Properties need freeing with mosquitto_property_free_all.

Requires the mosquitto instance to be connected with MQTT 5.

Parameters

mosqa valid mosquitto instance.
midpointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the publish callback to determine when the message has been sent.  Note that although the MQTT protocol doesn’t use message ids for messages with QoS=0, libmosquitto assigns them message ids so they can be tracked with this parameter.
topicnull terminated string of the topic to publish to.
payloadlenthe size of the payload (bytes).  Valid values are between 0 and 268,435,455.
payloadpointer to the data to send.  If payloadlen > 0 this must be a valid memory location.
qosinteger value 0, 1 or 2 indicating the Quality of Service to be used for the message.
retainset to true to make the message retained.
propertiesa valid mosquitto_property list, or NULL.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_PROTOCOLif there is a protocol error communicating with the broker.
MOSQ_ERR_PAYLOAD_SIZEif payloadlen is too large.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8
MOSQ_ERR_DUPLICATE_PROPERTYif a property is duplicated where it is forbidden.
MOSQ_ERR_PROTOCOLif any property is invalid for use with PUBLISH.
MOSQ_ERR_QOS_NOT_SUPPORTEDif the QoS is greater than that supported by the broker.
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

mosquitto_subscribe

libmosq_EXPORT int mosquitto_subscribe(struct mosquitto *mosq,
int *mid,
const char *sub,
int qos)

Subscribe to a topic.

Parameters

mosqa valid mosquitto instance.
mida pointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the subscribe callback to determine when the message has been sent.
subthe subscription pattern.
qosthe requested Quality of Service for this subscription.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

mosquitto_subscribe_v5

libmosq_EXPORT int mosquitto_subscribe_v5(struct mosquitto *mosq,
int *mid,
const char *sub,
int qos,
int options,
const mosquitto_property *properties)

Subscribe to a topic, with attached MQTT properties.

Use e.g.  mosquitto_property_add_string and similar to create a list of properties, then attach them to this publish.  Properties need freeing with mosquitto_property_free_all.

Requires the mosquitto instance to be connected with MQTT 5.

Parameters

mosqa valid mosquitto instance.
mida pointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the subscribe callback to determine when the message has been sent.
subthe subscription pattern.
qosthe requested Quality of Service for this subscription.
optionsoptions to apply to this subscription, OR’d together.  Set to 0 to use the default options, otherwise choose from the list: MQTT_SUB_OPT_NO_LOCAL: with this option set, if this client publishes to a topic to which it is subscribed, the broker will not publish the message back to the client.  MQTT_SUB_OPT_RETAIN_AS_PUBLISHED: with this option set, messages published for this subscription will keep the retain flag as was set by the publishing client.  The default behaviour without this option set has the retain flag indicating whether a message is fresh/stale.  MQTT_SUB_OPT_SEND_RETAIN_ALWAYS: with this option set, pre-existing retained messages are sent as soon as the subscription is made, even if the subscription already exists.  This is the default behaviour, so it is not necessary to set this option.  MQTT_SUB_OPT_SEND_RETAIN_NEW: with this option set, pre-existing retained messages for this subscription will be sent when the subscription is made, but only if the subscription does not already exist.  MQTT_SUB_OPT_SEND_RETAIN_NEVER: with this option set, pre-existing retained messages will never be sent for this subscription.
propertiesa valid mosquitto_property list, or NULL.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8
MOSQ_ERR_DUPLICATE_PROPERTYif a property is duplicated where it is forbidden.
MOSQ_ERR_PROTOCOLif any property is invalid for use with SUBSCRIBE.
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

mosquitto_subscribe_multiple

libmosq_EXPORT int mosquitto_subscribe_multiple(
   struct mosquitto *mosq,
   int *mid,
   int sub_count,
   char *const *const sub,
   int qos,
   int options,
   const mosquitto_property *properties
)

Subscribe to multiple topics.

Parameters

mosqa valid mosquitto instance.
mida pointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the subscribe callback to determine when the message has been sent.
sub_countthe count of subscriptions to be made
subarray of sub_count pointers, each pointing to a subscription string.  The “char *const const” datatype ensures that neither the array of pointers nor the strings that they point to are mutable.  If you aren’t familiar with this, just think of it as a safer “char *”, equivalent to “const char *” for a simple string pointer.
qosthe requested Quality of Service for each subscription.
optionsoptions to apply to this subscription, OR’d together.  This argument is not used for MQTT v3 susbcriptions.  Set to 0 to use the default options, otherwise choose from the list: MQTT_SUB_OPT_NO_LOCAL: with this option set, if this client publishes to a topic to which it is subscribed, the broker will not publish the message back to the client.  MQTT_SUB_OPT_RETAIN_AS_PUBLISHED: with this option set, messages published for this subscription will keep the retain flag as was set by the publishing client.  The default behaviour without this option set has the retain flag indicating whether a message is fresh/stale.  MQTT_SUB_OPT_SEND_RETAIN_ALWAYS: with this option set, pre-existing retained messages are sent as soon as the subscription is made, even if the subscription already exists.  This is the default behaviour, so it is not necessary to set this option.  MQTT_SUB_OPT_SEND_RETAIN_NEW: with this option set, pre-existing retained messages for this subscription will be sent when the subscription is made, but only if the subscription does not already exist.  MQTT_SUB_OPT_SEND_RETAIN_NEVER: with this option set, pre-existing retained messages will never be sent for this subscription.
propertiesa valid mosquitto_property list, or NULL.  Only used with MQTT v5 clients.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_MALFORMED_UTF8if a topic is not valid UTF-8
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

mosquitto_unsubscribe

libmosq_EXPORT int mosquitto_unsubscribe(struct mosquitto *mosq,
int *mid,
const char *sub)

Unsubscribe from a topic.

Parameters

mosqa valid mosquitto instance.
mida pointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the unsubscribe callback to determine when the message has been sent.
subthe unsubscription pattern.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

mosquitto_unsubscribe_v5

libmosq_EXPORT int mosquitto_unsubscribe_v5(
   struct mosquitto *mosq,
   int *mid,
   const char *sub,
   const mosquitto_property *properties
)

Unsubscribe from a topic, with attached MQTT properties.

Use e.g.  mosquitto_property_add_string and similar to create a list of properties, then attach them to this publish.  Properties need freeing with mosquitto_property_free_all.

Parameters

mosqa valid mosquitto instance.
mida pointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the unsubscribe callback to determine when the message has been sent.
subthe unsubscription pattern.
propertiesa valid mosquitto_property list, or NULL.  Only used with MQTT v5 clients.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8
MOSQ_ERR_DUPLICATE_PROPERTYif a property is duplicated where it is forbidden.
MOSQ_ERR_PROTOCOLif any property is invalid for use with UNSUBSCRIBE.
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

mosquitto_unsubscribe_multiple

libmosq_EXPORT int mosquitto_unsubscribe_multiple(
   struct mosquitto *mosq,
   int *mid,
   int sub_count,
   char *const *const sub,
   const mosquitto_property *properties
)

Unsubscribe from multiple topics.

Parameters

mosqa valid mosquitto instance.
mida pointer to an int.  If not NULL, the function will set this to the message id of this particular message.  This can be then used with the subscribe callback to determine when the message has been sent.
sub_countthe count of unsubscriptions to be made
subarray of sub_count pointers, each pointing to an unsubscription string.  The “char *const const” datatype ensures that neither the array of pointers nor the strings that they point to are mutable.  If you aren’t familiar with this, just think of it as a safer “char *”, equivalent to “const char *” for a simple string pointer.
propertiesa valid mosquitto_property list, or NULL.  Only used with MQTT v5 clients.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_MALFORMED_UTF8if a topic is not valid UTF-8
MOSQ_ERR_OVERSIZE_PACKETif the resulting packet would be larger than supported by the broker.

Struct mosquitto_message helper functions

Summary
Functions
mosquitto_message_copyCopy the contents of a mosquitto message to another message.
mosquitto_message_freeCompletely free a mosquitto_message struct.
mosquitto_message_free_contentsFree a mosquitto_message struct contents, leaving the struct unaffected.

Functions

mosquitto_message_copy

libmosq_EXPORT int mosquitto_message_copy(struct mosquitto_message *dst,
const struct mosquitto_message *src)

Copy the contents of a mosquitto message to another message.  Useful for preserving a message received in the on_message() callback.

Parameters

dsta pointer to a valid mosquitto_message struct to copy to.
srca pointer to a valid mosquitto_message struct to copy from.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

See Also

mosquitto_message_free

mosquitto_message_free

libmosq_EXPORT void mosquitto_message_free(struct mosquitto_message **message)

Completely free a mosquitto_message struct.

Parameters

messagepointer to a mosquitto_message pointer to free.

See Also

mosquitto_message_copy, mosquitto_message_free_contents

mosquitto_message_free_contents

libmosq_EXPORT void mosquitto_message_free_contents(
   struct mosquitto_message *message
)

Free a mosquitto_message struct contents, leaving the struct unaffected.

Parameters

messagepointer to a mosquitto_message struct to free its contents.

See Also

mosquitto_message_copy, mosquitto_message_free

Network loop (managed by libmosquitto)

The internal network loop must be called at a regular interval.  The two recommended approaches are to use either mosquitto_loop_forever or mosquitto_loop_startmosquitto_loop_forever is a blocking call and is suitable for the situation where you only want to handle incoming messages in callbacks.  mosquitto_loop_start is a non-blocking call, it creates a separate thread to run the loop for you.  Use this function when you have other tasks you need to run at the same time as the MQTT client, e.g. reading data from a sensor.

Summary
Functions
mosquitto_loop_foreverThis function call loop() for you in an infinite blocking loop.
mosquitto_loop_startThis is part of the threaded client interface.
mosquitto_loop_stopThis is part of the threaded client interface.
mosquitto_loopThe main network loop for the client.

Functions

mosquitto_loop_forever

libmosq_EXPORT int mosquitto_loop_forever(struct mosquitto *mosq,
int timeout,
int max_packets)

This function call loop() for you in an infinite blocking loop.  It is useful for the case where you only want to run the MQTT client loop in your program.

It handles reconnecting in case server connection is lost.  If you call mosquitto_disconnect() in a callback it will return.

Parameters

mosqa valid mosquitto instance.
timeoutMaximum number of milliseconds to wait for network activity in the select() call before timing out.  Set to 0 for instant return.  Set negative to use the default of 1000ms.
max_packetsthis parameter is currently unused and should be set to 1 for future compatibility.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_CONN_LOSTif the connection to the broker was lost.
MOSQ_ERR_PROTOCOLif there is a protocol error communicating with the broker.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_loop, mosquitto_loop_start

mosquitto_loop_start

libmosq_EXPORT int mosquitto_loop_start(struct mosquitto *mosq)

This is part of the threaded client interface.  Call this once to start a new thread to process network traffic.  This provides an alternative to repeatedly calling mosquitto_loop yourself.

Parameters

mosqa valid mosquitto instance.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOT_SUPPORTEDif thread support is not available.

See Also

mosquitto_connect_async, mosquitto_loop, mosquitto_loop_forever, mosquitto_loop_stop

mosquitto_loop_stop

libmosq_EXPORT int mosquitto_loop_stop(struct mosquitto *mosq,
bool force)

This is part of the threaded client interface.  Call this once to stop the network thread previously created with mosquitto_loop_start.  This call will block until the network thread finishes.  For the network thread to end, you must have previously called mosquitto_disconnect or have set the force parameter to true.

Parameters

mosqa valid mosquitto instance.
forceset to true to force thread cancellation.  If false, mosquitto_disconnect must have already been called.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOT_SUPPORTEDif thread support is not available.

See Also

mosquitto_loop, mosquitto_loop_start

mosquitto_loop

libmosq_EXPORT int mosquitto_loop(struct mosquitto *mosq,
int timeout,
int max_packets)

The main network loop for the client.  This must be called frequently to keep communications between the client and broker working.  This is carried out by mosquitto_loop_forever and mosquitto_loop_start, which are the recommended ways of handling the network loop.  You may also use this function if you wish.  It must not be called inside a callback.

If incoming data is present it will then be processed.  Outgoing commands, from e.g.  mosquitto_publish, are normally sent immediately that their function is called, but this is not always possible.  mosquitto_loop will also attempt to send any remaining outgoing messages, which also includes commands that are part of the flow for messages with QoS>0.

This calls select() to monitor the client network socket.  If you want to integrate mosquitto client operation with your own select() call, use mosquitto_socket, mosquitto_loop_read, mosquitto_loop_write and mosquitto_loop_misc.

Threads

Parameters

mosqa valid mosquitto instance.
timeoutMaximum number of milliseconds to wait for network activity in the select() call before timing out.  Set to 0 for instant return.  Set negative to use the default of 1000ms.
max_packetsthis parameter is currently unused and should be set to 1 for future compatibility.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_CONN_LOSTif the connection to the broker was lost.
MOSQ_ERR_PROTOCOLif there is a protocol error communicating with the broker.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.  See Also: mosquitto_loop_forever, mosquitto_loop_start, mosquitto_loop_stop

Network loop (for use in other event loops)

Summary
Functions
mosquitto_loop_readCarry out network read operations.
mosquitto_loop_writeCarry out network write operations.
mosquitto_loop_miscCarry out miscellaneous operations required as part of the network loop.

Functions

mosquitto_loop_read

libmosq_EXPORT int mosquitto_loop_read(struct mosquitto *mosq,
int max_packets)

Carry out network read operations.  This should only be used if you are not using mosquitto_loop() and are monitoring the client network socket for activity yourself.

Parameters

mosqa valid mosquitto instance.
max_packetsthis parameter is currently unused and should be set to 1 for future compatibility.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_CONN_LOSTif the connection to the broker was lost.
MOSQ_ERR_PROTOCOLif there is a protocol error communicating with the broker.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_socket, mosquitto_loop_write, mosquitto_loop_misc

mosquitto_loop_write

libmosq_EXPORT int mosquitto_loop_write(struct mosquitto *mosq,
int max_packets)

Carry out network write operations.  This should only be used if you are not using mosquitto_loop() and are monitoring the client network socket for activity yourself.

Parameters

mosqa valid mosquitto instance.
max_packetsthis parameter is currently unused and should be set to 1 for future compatibility.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.
MOSQ_ERR_CONN_LOSTif the connection to the broker was lost.
MOSQ_ERR_PROTOCOLif there is a protocol error communicating with the broker.
MOSQ_ERR_ERRNOif a system call returned an error.  The variable errno contains the error code, even on Windows.  Use strerror_r() where available or FormatMessage() on Windows.

See Also

mosquitto_socket, mosquitto_loop_read, mosquitto_loop_misc, mosquitto_want_write

mosquitto_loop_misc

libmosq_EXPORT int mosquitto_loop_misc(struct mosquitto *mosq)

Carry out miscellaneous operations required as part of the network loop.  This should only be used if you are not using mosquitto_loop() and are monitoring the client network socket for activity yourself.

This function deals with handling PINGs and checking whether messages need to be retried, so should be called fairly frequently, around once per second is sufficient.

Parameters

mosqa valid mosquitto instance.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NO_CONNif the client isn’t connected to a broker.

See Also

mosquitto_socket, mosquitto_loop_read, mosquitto_loop_write

Network loop (helper functions)

Summary
Functions
mosquitto_socketReturn the socket handle for a mosquitto instance.
mosquitto_want_writeReturns true if there is data ready to be written on the socket.
mosquitto_threaded_setUsed to tell the library that your application is using threads, but not using mosquitto_loop_start.

Functions

mosquitto_socket

libmosq_EXPORT int mosquitto_socket(struct mosquitto *mosq)

Return the socket handle for a mosquitto instance.  Useful if you want to include a mosquitto client in your own select() calls.

Parameters

mosqa valid mosquitto instance.

Returns

The socket for the mosquitto client or -1 on failure.

mosquitto_want_write

libmosq_EXPORT bool mosquitto_want_write(struct mosquitto *mosq)

Returns true if there is data ready to be written on the socket.

Parameters

mosqa valid mosquitto instance.

See Also

mosquitto_socket, mosquitto_loop_read, mosquitto_loop_write

mosquitto_threaded_set

libmosq_EXPORT int mosquitto_threaded_set(struct mosquitto *mosq,
bool threaded)

Used to tell the library that your application is using threads, but not using mosquitto_loop_start.  The library operates slightly differently when not in threaded mode in order to simplify its operation.  If you are managing your own threads and do not use this function you will experience crashes due to race conditions.

When using mosquitto_loop_start, this is set automatically.

Parameters

mosqa valid mosquitto instance.
threadedtrue if your application is using threads, false otherwise.

Client options

Summary
Functions
mosquitto_opts_setUsed to set options for the client.
mosquitto_int_optionUsed to set integer options for the client.
mosquitto_void_optionUsed to set void* options for the client.
mosquitto_reconnect_delay_setControl the behaviour of the client when it has unexpectedly disconnected in mosquitto_loop_forever or after mosquitto_loop_start.
mosquitto_max_inflight_messages_setThis function is deprected.
mosquitto_message_retry_setThis function now has no effect.
mosquitto_user_data_setWhen mosquitto_new is called, the pointer given as the “obj” parameter will be passed to the callbacks as user data.
mosquitto_userdataRetrieve the “userdata” variable for a mosquitto client.

Functions

mosquitto_opts_set

libmosq_EXPORT int mosquitto_opts_set(struct mosquitto *mosq,
enum mosq_opt_t option,
void *value)

Used to set options for the client.

This function is deprecated, the replacement mosquitto_int_option and mosquitto_void_option functions should be used instead.

Parameters

mosqa valid mosquitto instance.
optionthe option to set.
valuethe option specific value.

Options

MOSQ_OPT_PROTOCOL_VERSION Value must be an int, set to either MQTT_PROTOCOL_V31 or MQTT_PROTOCOL_V311.  Must be set before the client connects.  Defaults to MQTT_PROTOCOL_V31.

MOSQ_OPT_SSL_CTX Pass an openssl SSL_CTX to be used when creating TLS connections rather than libmosquitto creating its own.  This must be called before connecting to have any effect.  If you use this option, the onus is on you to ensure that you are using secure settings.  Setting to NULL means that libmosquitto will use its own SSL_CTX if TLS is to be used.  This option is only available for openssl 1.1.0 and higher.

MOSQ_OPT_SSL_CTX_WITH_DEFAULTS Value must be an int set to 1 or 0.  If set to 1, then the user specified SSL_CTX passed in using MOSQ_OPT_SSL_CTX will have the default options applied to it.  This means that you only need to change the values that are relevant to you.  If you use this option then you must configure the TLS options as normal, i.e. you should use mosquitto_tls_set to configure the cafile/capath as a minimum.  This option is only available for openssl 1.1.0 and higher.

mosquitto_int_option

libmosq_EXPORT int mosquitto_int_option(struct mosquitto *mosq,
enum mosq_opt_t option,
int value)

Used to set integer options for the client.

Parameters

mosqa valid mosquitto instance.
optionthe option to set.
valuethe option specific value.

Options

MOSQ_OPT_PROTOCOL_VERSION - Value must be set to either MQTT_PROTOCOL_V31, MQTT_PROTOCOL_V311, or MQTT_PROTOCOL_V5.  Must be set before the client connects.  Defaults to MQTT_PROTOCOL_V311.

MOSQ_OPT_RECEIVE_MAXIMUM - Value can be set between 1 and 65535 inclusive, and represents the maximum number of incoming QoS 1 and QoS 2 messages that this client wants to process at once.  Defaults to 20.  This option is not valid for MQTT v3.1 or v3.1.1 clients.  Note that if the MQTT_PROP_RECEIVE_MAXIMUM property is in the proplist passed to mosquitto_connect_v5(), then that property will override this option.  Using this option is the recommended method however.

MOSQ_OPT_SEND_MAXIMUM - Value can be set between 1 and 65535 inclusive, and represents the maximum number of outgoing QoS 1 and QoS 2 messages that this client will attempt to have “in flight” at once.  Defaults to 20.  This option is not valid for MQTT v3.1 or v3.1.1 clients.  Note that if the broker being connected to sends a MQTT_PROP_RECEIVE_MAXIMUM property that has a lower value than this option, then the broker provided value will be used.

MOSQ_OPT_SSL_CTX_WITH_DEFAULTS - If value is set to a non zero value, then the user specified SSL_CTX passed in using MOSQ_OPT_SSL_CTX will have the default options applied to it.  This means that you only need to change the values that are relevant to you.  If you use this option then you must configure the TLS options as normal, i.e.  you should use mosquitto_tls_set to configure the cafile/capath as a minimum.  This option is only available for openssl 1.1.0 and higher.

MOSQ_OPT_TLS_OCSP_REQUIRED - Set whether OCSP checking on TLS connections is required.  Set to 1 to enable checking, or 0 (the default) for no checking.

mosquitto_void_option

libmosq_EXPORT int mosquitto_void_option(struct mosquitto *mosq,
enum mosq_opt_t option,
void *value)

Used to set void* options for the client.

Parameters

mosqa valid mosquitto instance.
optionthe option to set.
valuethe option specific value.

Options

MOSQ_OPT_SSL_CTX - Pass an openssl SSL_CTX to be used when creating TLS connections rather than libmosquitto creating its own.  This must be called before connecting to have any effect.  If you use this option, the onus is on you to ensure that you are using secure settings.  Setting to NULL means that libmosquitto will use its own SSL_CTX if TLS is to be used.  This option is only available for openssl 1.1.0 and higher.

mosquitto_reconnect_delay_set

libmosq_EXPORT int mosquitto_reconnect_delay_set(
   struct mosquitto *mosq,
   unsigned int reconnect_delay,
   unsigned int reconnect_delay_max,
   bool reconnect_exponential_backoff
)

Control the behaviour of the client when it has unexpectedly disconnected in mosquitto_loop_forever or after mosquitto_loop_start.  The default behaviour if this function is not used is to repeatedly attempt to reconnect with a delay of 1 second until the connection succeeds.

Use reconnect_delay parameter to change the delay between successive reconnection attempts.  You may also enable exponential backoff of the time between reconnections by setting reconnect_exponential_backoff to true and set an upper bound on the delay with reconnect_delay_max.

Example 1

delay=2, delay_max=10, exponential_backoff=False Delays would be: 2, 4, 6, 8, 10, 10, ...

Example 2

delay=3, delay_max=30, exponential_backoff=True Delays would be: 3, 6, 12, 24, 30, 30, ...

Parameters

mosqa valid mosquitto instance.
reconnect_delaythe number of seconds to wait between reconnects.
reconnect_delay_maxthe maximum number of seconds to wait between reconnects.
reconnect_exponential_backoffuse exponential backoff between reconnect attempts.  Set to true to enable exponential backoff.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.

mosquitto_max_inflight_messages_set

libmosq_EXPORT int mosquitto_max_inflight_messages_set(
   struct mosquitto *mosq,
   unsigned int max_inflight_messages
)

This function is deprected.  Use the mosquitto_int_option function with the MOSQ_OPT_SEND_MAXIMUM option instead.

Set the number of QoS 1 and 2 messages that can be “in flight” at one time.  An in flight message is part way through its delivery flow.  Attempts to send further messages with mosquitto_publish will result in the messages being queued until the number of in flight messages reduces.

A higher number here results in greater message throughput, but if set higher than the maximum in flight messages on the broker may lead to delays in the messages being acknowledged.

Set to 0 for no maximum.

Parameters

mosqa valid mosquitto instance.
max_inflight_messagesthe maximum number of inflight messages.  Defaults to 20.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.

mosquitto_message_retry_set

libmosq_EXPORT void mosquitto_message_retry_set(struct mosquitto *mosq,
unsigned int message_retry)

This function now has no effect.

mosquitto_user_data_set

libmosq_EXPORT void mosquitto_user_data_set(struct mosquitto *mosq,
void *obj)

When mosquitto_new is called, the pointer given as the “obj” parameter will be passed to the callbacks as user data.  The mosquitto_user_data_set function allows this obj parameter to be updated at any time.  This function will not modify the memory pointed to by the current user data pointer.  If it is dynamically allocated memory you must free it yourself.

Parameters

mosqa valid mosquitto instance.
objA user pointer that will be passed as an argument to any callbacks that are specified.

mosquitto_userdata

libmosq_EXPORT void *mosquitto_userdata(struct mosquitto *mosq)

Retrieve the “userdata” variable for a mosquitto client.

Parameters

mosqa valid mosquitto instance.

Returns

A pointer to the userdata member variable.

TLS support

Summary
Functions
mosquitto_tls_setConfigure the client for certificate based SSL/TLS support.
mosquitto_tls_insecure_setConfigure verification of the server hostname in the server certificate.
mosquitto_tls_opts_setSet advanced SSL/TLS options.
mosquitto_tls_psk_setConfigure the client for pre-shared-key based TLS support.

Functions

mosquitto_tls_set

libmosq_EXPORT int mosquitto_tls_set(
   struct mosquitto *mosq,
   const char *cafile,
   const char *capath,
   const char *certfile,
   const char *keyfile,
   int (*pw_callback)(char *buf, int size, int rwflag, void *userdata)
)

Configure the client for certificate based SSL/TLS support.  Must be called before mosquitto_connect.

Cannot be used in conjunction with mosquitto_tls_psk_set.

Define the Certificate Authority certificates to be trusted (ie. the server certificate must be signed with one of these certificates) using cafile.

If the server you are connecting to requires clients to provide a certificate, define certfile and keyfile with your client certificate and private key.  If your private key is encrypted, provide a password callback function or you will have to enter the password at the command line.

Parameters

mosqa valid mosquitto instance.
cafilepath to a file containing the PEM encoded trusted CA certificate files.  Either cafile or capath must not be NULL.
capathpath to a directory containing the PEM encoded trusted CA certificate files.  See mosquitto.conf for more details on configuring this directory.  Either cafile or capath must not be NULL.
certfilepath to a file containing the PEM encoded certificate file for this client.  If NULL, keyfile must also be NULL and no client certificate will be used.
keyfilepath to a file containing the PEM encoded private key for this client.  If NULL, certfile must also be NULL and no client certificate will be used.
pw_callbackif keyfile is encrypted, set pw_callback to allow your client to pass the correct password for decryption.  If set to NULL, the password must be entered on the command line.  Your callback must write the password into “buf”, which is “size” bytes long.  The return value must be the length of the password.  “userdata” will be set to the calling mosquitto instance.  The mosquitto userdata member variable can be retrieved using mosquitto_userdata.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

See Also

mosquitto_tls_opts_set, mosquitto_tls_psk_set, mosquitto_tls_insecure_set, mosquitto_userdata

mosquitto_tls_insecure_set

libmosq_EXPORT int mosquitto_tls_insecure_set(struct mosquitto *mosq,
bool value)

Configure verification of the server hostname in the server certificate.  If value is set to true, it is impossible to guarantee that the host you are connecting to is not impersonating your server.  This can be useful in initial server testing, but makes it possible for a malicious third party to impersonate your server through DNS spoofing, for example.  Do not use this function in a real system.  Setting value to true makes the connection encryption pointless.  Must be called before mosquitto_connect.

Parameters

mosqa valid mosquitto instance.
valueif set to false, the default, certificate hostname checking is performed.  If set to true, no hostname checking is performed and the connection is insecure.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.

See Also

mosquitto_tls_set

mosquitto_tls_opts_set

libmosq_EXPORT int mosquitto_tls_opts_set(struct mosquitto *mosq,
int cert_reqs,
const char *tls_version,
const char *ciphers)

Set advanced SSL/TLS options.  Must be called before mosquitto_connect.

Parameters

mosqa valid mosquitto instance.
cert_reqsan integer defining the verification requirements the client will impose on the server.  This can be one of:
  • SSL_VERIFY_NONE (0): the server will not be verified in any way.
  • SSL_VERIFY_PEER (1): the server certificate will be verified and the connection aborted if the verification fails.  The default and recommended value is SSL_VERIFY_PEER.  Using SSL_VERIFY_NONE provides no security.
tls_versionthe version of the SSL/TLS protocol to use as a string.  If NULL, the default value is used.  The default value and the available values depend on the version of openssl that the library was compiled against.  For openssl >= 1.0.1, the available options are tlsv1.2, tlsv1.1 and tlsv1, with tlv1.2 as the default.  For openssl < 1.0.1, only tlsv1 is available.
ciphersa string describing the ciphers available for use.  See the “openssl ciphers” tool for more information.  If NULL, the default ciphers will be used.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

See Also

mosquitto_tls_set

mosquitto_tls_psk_set

libmosq_EXPORT int mosquitto_tls_psk_set(struct mosquitto *mosq,
const char *psk,
const char *identity,
const char *ciphers)

Configure the client for pre-shared-key based TLS support.  Must be called before mosquitto_connect.

Cannot be used in conjunction with mosquitto_tls_set.

Parameters

mosqa valid mosquitto instance.
pskthe pre-shared-key in hex format with no leading “0x”.
identitythe identity of this client.  May be used as the username depending on the server settings.
ciphersa string describing the PSK ciphers available for use.  See the “openssl ciphers” tool for more information.  If NULL, the default ciphers will be used.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

See Also

mosquitto_tls_set

Callbacks

Summary
Functions
mosquitto_connect_callback_setSet the connect callback.
mosquitto_connect_with_flags_callback_setSet the connect callback.
mosquitto_connect_v5_callback_setSet the connect callback.
mosquitto_disconnect_callback_setSet the disconnect callback.
mosquitto_disconnect_v5_callback_setSet the disconnect callback.
mosquitto_publish_callback_setSet the publish callback.
mosquitto_publish_v5_callback_setSet the publish callback.
mosquitto_message_callback_setSet the message callback.
mosquitto_message_v5_callback_setSet the message callback.
mosquitto_subscribe_callback_setSet the subscribe callback.
mosquitto_subscribe_v5_callback_setSet the subscribe callback.
mosquitto_unsubscribe_callback_setSet the unsubscribe callback.
mosquitto_unsubscribe_v5_callback_setSet the unsubscribe callback.
mosquitto_log_callback_setSet the logging callback.
mosquitto_string_optionUsed to set const char* options for the client.
mosquitto_reconnect_delay_setControl the behaviour of the client when it has unexpectedly disconnected in mosquitto_loop_forever or after mosquitto_loop_start.

Functions

mosquitto_connect_callback_set

libmosq_EXPORT void mosquitto_connect_callback_set(
   struct mosquitto *mosq,
   void (*on_connect)(struct mosquitto *, void *, int)
)

Set the connect callback.  This is called when the broker sends a CONNACK message in response to a connection.

Parameters

mosqa valid mosquitto instance.
on_connecta callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int rc)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
rcthe return code of the connection response, one of:
  • 0 - success
  • 1 - connection refused (unacceptable protocol version)
  • 2 - connection refused (identifier rejected)
  • 3 - connection refused (broker unavailable)
  • 4-255 - reserved for future use

mosquitto_connect_with_flags_callback_set

libmosq_EXPORT void mosquitto_connect_with_flags_callback_set(
   struct mosquitto *mosq,
   void (*on_connect)(struct mosquitto *, void *, int, int)
)

Set the connect callback.  This is called when the broker sends a CONNACK message in response to a connection.

Parameters

mosqa valid mosquitto instance.
on_connecta callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int rc)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
rcthe return code of the connection response, one of:
flagsthe connect flags.
  • 0 - success
  • 1 - connection refused (unacceptable protocol version)
  • 2 - connection refused (identifier rejected)
  • 3 - connection refused (broker unavailable)
  • 4-255 - reserved for future use

mosquitto_connect_v5_callback_set

libmosq_EXPORT void mosquitto_connect_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_connect)(struct mosquitto *, void *, int, int, const mosquitto_property *props)
)

Set the connect callback.  This is called when the broker sends a CONNACK message in response to a connection.

Parameters

mosqa valid mosquitto instance.
on_connecta callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int rc)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
rcthe return code of the connection response, one of:
  • 0 - success
  • 1 - connection refused (unacceptable protocol version)
  • 2 - connection refused (identifier rejected)
  • 3 - connection refused (broker unavailable)
  • 4-255 - reserved for future use
flagsthe connect flags.
propslist of MQTT 5 properties, or NULL

mosquitto_disconnect_callback_set

libmosq_EXPORT void mosquitto_disconnect_callback_set(
   struct mosquitto *mosq,
   void (*on_disconnect)(struct mosquitto *, void *, int)
)

Set the disconnect callback.  This is called when the broker has received the DISCONNECT command and has disconnected the client.

Parameters

mosqa valid mosquitto instance.
on_disconnecta callback function in the following form: void callback(struct mosquitto *mosq, void *obj)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
rcinteger value indicating the reason for the disconnect.  A value of 0 means the client has called mosquitto_disconnect.  Any other value indicates that the disconnect is unexpected.

mosquitto_disconnect_v5_callback_set

libmosq_EXPORT void mosquitto_disconnect_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_disconnect)(struct mosquitto *, void *, int, const mosquitto_property *)
)

Set the disconnect callback.  This is called when the broker has received the DISCONNECT command and has disconnected the client.

Parameters

mosqa valid mosquitto instance.
on_disconnecta callback function in the following form: void callback(struct mosquitto *mosq, void *obj)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
rcinteger value indicating the reason for the disconnect.  A value of 0 means the client has called mosquitto_disconnect.  Any other value indicates that the disconnect is unexpected.
propslist of MQTT 5 properties, or NULL

mosquitto_publish_callback_set

libmosq_EXPORT void mosquitto_publish_callback_set(
   struct mosquitto *mosq,
   void (*on_publish)(struct mosquitto *, void *, int)
)

Set the publish callback.  This is called when a message initiated with mosquitto_publish has been sent to the broker successfully.

Parameters

mosqa valid mosquitto instance.
on_publisha callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int mid)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
midthe message id of the sent message.

mosquitto_publish_v5_callback_set

libmosq_EXPORT void mosquitto_publish_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_publish)(struct mosquitto *, void *, int, int, const mosquitto_property *)
)

Set the publish callback.  This is called when a message initiated with mosquitto_publish has been sent to the broker.  This callback will be called both if the message is sent successfully, or if the broker responded with an error, which will be reflected in the reason_code parameter.

Parameters

mosqa valid mosquitto instance.
on_publisha callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int mid)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
midthe message id of the sent message.
reason_codethe MQTT 5 reason code
propslist of MQTT 5 properties, or NULL

mosquitto_message_callback_set

libmosq_EXPORT void mosquitto_message_callback_set(
   struct mosquitto *mosq,
   void (*on_message)(struct mosquitto *, void *, const struct mosquitto_message *)
)

Set the message callback.  This is called when a message is received from the broker.

Parameters

mosqa valid mosquitto instance.
on_messagea callback function in the following form: void callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
messagethe message data.  This variable and associated memory will be freed by the library after the callback completes.  The client should make copies of any of the data it requires.

See Also

mosquitto_message_copy

mosquitto_message_v5_callback_set

libmosq_EXPORT void mosquitto_message_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_message)(struct mosquitto *, void *, const struct mosquitto_message *, const mosquitto_property *)
)

Set the message callback.  This is called when a message is received from the broker.

Parameters

mosqa valid mosquitto instance.
on_messagea callback function in the following form: void callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
messagethe message data.  This variable and associated memory will be freed by the library after the callback completes.  The client should make copies of any of the data it requires.
propslist of MQTT 5 properties, or NULL

See Also

mosquitto_message_copy

mosquitto_subscribe_callback_set

libmosq_EXPORT void mosquitto_subscribe_callback_set(
   struct mosquitto *mosq,
   void (*on_subscribe)(struct mosquitto *, void *, int, int, const int *)
)

Set the subscribe callback.  This is called when the broker responds to a subscription request.

Parameters

mosqa valid mosquitto instance.
on_subscribea callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
midthe message id of the subscribe message.
qos_countthe number of granted subscriptions (size of granted_qos).
granted_qosan array of integers indicating the granted QoS for each of the subscriptions.

mosquitto_subscribe_v5_callback_set

libmosq_EXPORT void mosquitto_subscribe_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_subscribe)(struct mosquitto *, void *, int, int, const int *, const mosquitto_property *)
)

Set the subscribe callback.  This is called when the broker responds to a subscription request.

Parameters

mosqa valid mosquitto instance.
on_subscribea callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
midthe message id of the subscribe message.
qos_countthe number of granted subscriptions (size of granted_qos).
granted_qosan array of integers indicating the granted QoS for each of the subscriptions.
propslist of MQTT 5 properties, or NULL

mosquitto_unsubscribe_callback_set

libmosq_EXPORT void mosquitto_unsubscribe_callback_set(
   struct mosquitto *mosq,
   void (*on_unsubscribe)(struct mosquitto *, void *, int)
)

Set the unsubscribe callback.  This is called when the broker responds to a unsubscription request.

Parameters

mosqa valid mosquitto instance.
on_unsubscribea callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int mid)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
midthe message id of the unsubscribe message.

mosquitto_unsubscribe_v5_callback_set

libmosq_EXPORT void mosquitto_unsubscribe_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_unsubscribe)(struct mosquitto *, void *, int, const mosquitto_property *)
)

Set the unsubscribe callback.  This is called when the broker responds to a unsubscription request.

Parameters

mosqa valid mosquitto instance.
on_unsubscribea callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int mid)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
midthe message id of the unsubscribe message.
propslist of MQTT 5 properties, or NULL

mosquitto_log_callback_set

libmosq_EXPORT void mosquitto_log_callback_set(
   struct mosquitto *mosq,
   void (*on_log)(struct mosquitto *, void *, int, const char *)
)

Set the logging callback.  This should be used if you want event logging information from the client library.

mosqa valid mosquitto instance.
on_loga callback function in the following form: void callback(struct mosquitto *mosq, void *obj, int level, const char *str)

Callback Parameters

mosqthe mosquitto instance making the callback.
objthe user data provided in mosquitto_new
levelthe log message level from the values: MOSQ_LOG_INFO MOSQ_LOG_NOTICE MOSQ_LOG_WARNING MOSQ_LOG_ERR MOSQ_LOG_DEBUG
strthe message string.

mosquitto_string_option

libmosq_EXPORT int mosquitto_string_option(struct mosquitto *mosq,
enum mosq_opt_t option,
const char *value)

Used to set const char* options for the client.

Parameters

mosqa valid mosquitto instance.
optionthe option to set.
valuethe option specific value.

Options

MOSQ_OPT_TLS_ENGINE Configure the client for TLS Engine support.  Pass a TLS Engine ID to be used when creating TLS connections.  Must be set before mosquitto_connect.  MOSQ_OPT_TLS_KEYFORM Configure the client to treat the keyfile differently depending on its type.  Must be set before mosquitto_connect.  Set as either “pem” or “engine”, to determine from where the private key for a TLS connection will be obtained.  Defaults to “pem”, a normal private key file.  MOSQ_OPT_TLS_KPASS_SHA1 Where the TLS Engine requires the use of a password to be accessed, this option allows a hex encoded SHA1 hash of the private key password to be passed to the engine directly.  Must be set before mosquitto_connect.  MOSQ_OPT_TLS_ALPN If the broker being connected to has multiple services available on a single TLS port, such as both MQTT and WebSockets, use this option to configure the ALPN option for the connection.

mosquitto_reconnect_delay_set

libmosq_EXPORT int mosquitto_reconnect_delay_set(
   struct mosquitto *mosq,
   unsigned int reconnect_delay,
   unsigned int reconnect_delay_max,
   bool reconnect_exponential_backoff
)

Control the behaviour of the client when it has unexpectedly disconnected in mosquitto_loop_forever or after mosquitto_loop_start.  The default behaviour if this function is not used is to repeatedly attempt to reconnect with a delay of 1 second until the connection succeeds.

Use reconnect_delay parameter to change the delay between successive reconnection attempts.  You may also enable exponential backoff of the time between reconnections by setting reconnect_exponential_backoff to true and set an upper bound on the delay with reconnect_delay_max.

Example 1

delay=2, delay_max=10, exponential_backoff=False Delays would be: 2, 4, 6, 8, 10, 10, ...

Example 2

delay=3, delay_max=30, exponential_backoff=True Delays would be: 3, 6, 12, 24, 30, 30, ...

Parameters

mosqa valid mosquitto instance.
reconnect_delaythe number of seconds to wait between reconnects.
reconnect_delay_maxthe maximum number of seconds to wait between reconnects.
reconnect_exponential_backoffuse exponential backoff between reconnect attempts.  Set to true to enable exponential backoff.

Returns

MOSQ_ERR_SUCCESSon success.
MOSQ_ERR_INVALif the input parameters were invalid.

SOCKS5 proxy functions

Summary
Functions
mosquitto_socks5_setConfigure the client to use a SOCKS5 proxy when connecting.

Functions

mosquitto_socks5_set

libmosq_EXPORT int mosquitto_socks5_set(struct mosquitto *mosq,
const char *host,
int port,
const char *username,
const char *password)

Configure the client to use a SOCKS5 proxy when connecting.  Must be called before connecting.  “None” and “username/password” authentication is supported.

Parameters

mosqa valid mosquitto instance.
hostthe SOCKS5 proxy host to connect to.
portthe SOCKS5 proxy port to use.
usernameif not NULL, use this username when authenticating with the proxy.
passwordif not NULL and username is not NULL, use this password when authenticating with the proxy.

Utility functions

Summary
Functions
mosquitto_strerrorCall to obtain a const string description of a mosquitto error number.
mosquitto_connack_stringCall to obtain a const string description of an MQTT connection result.
mosquitto_reason_stringCall to obtain a const string description of an MQTT reason code.
mosquitto_string_to_commandTake a string input representing an MQTT command and convert it to the libmosquitto integer representation.
mosquitto_sub_topic_tokeniseTokenise a topic or subscription string into an array of strings representing the topic hierarchy.
mosquitto_sub_topic_tokens_freeFree memory that was allocated in mosquitto_sub_topic_tokenise.
mosquitto_topic_matches_subCheck whether a topic matches a subscription.
mosquitto_topic_matches_sub2Check whether a topic matches a subscription.
mosquitto_pub_topic_checkCheck whether a topic to be used for publishing is valid.
mosquitto_pub_topic_check2Check whether a topic to be used for publishing is valid.
mosquitto_sub_topic_checkCheck whether a topic to be used for subscribing is valid.
mosquitto_sub_topic_check2Check whether a topic to be used for subscribing is valid.
mosquitto_validate_utf8Helper function to validate whether a UTF-8 string is valid, according to the UTF-8 spec and the MQTT additions.

Functions

mosquitto_strerror

libmosq_EXPORT const char *mosquitto_strerror(int mosq_errno)

Call to obtain a const string description of a mosquitto error number.

Parameters

mosq_errnoa mosquitto error number.

Returns

A constant string describing the error.

mosquitto_connack_string

libmosq_EXPORT const char *mosquitto_connack_string(int connack_code)

Call to obtain a const string description of an MQTT connection result.

Parameters

connack_codean MQTT connection result.

Returns

A constant string describing the result.

mosquitto_reason_string

libmosq_EXPORT const char *mosquitto_reason_string(int reason_code)

Call to obtain a const string description of an MQTT reason code.

Parameters

reason_codean MQTT reason code.

Returns

A constant string describing the reason.

mosquitto_string_to_command

libmosq_EXPORT int mosquitto_string_to_command(const char *str,
int *cmd)

Take a string input representing an MQTT command and convert it to the libmosquitto integer representation.

Parameters

strthe string to parse.
cmdpointer to an int, for the result.

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALon an invalid input.

Example

mosquitto_string_to_command(“CONNECT”, &cmd); // cmd == CMD_CONNECT

mosquitto_sub_topic_tokenise

libmosq_EXPORT int mosquitto_sub_topic_tokenise(const char *subtopic,
char ***topics,
int *count)

Tokenise a topic or subscription string into an array of strings representing the topic hierarchy.

For example

subtopic: “a/deep/topic/hierarchy”

Would result in

topics[0] = “a” topics[1] = “deep” topics[2] = “topic” topics[3] = “hierarchy”

and

subtopic: “/a/deep/topic/hierarchy/”

Would result in

topics[0] = NULL topics[1] = “a” topics[2] = “deep” topics[3] = “topic” topics[4] = “hierarchy”

Parameters

subtopicthe subscription/topic to tokenise
topicsa pointer to store the array of strings
countan int pointer to store the number of items in the topics array.

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_NOMEMif an out of memory condition occurred.
MOSQ_ERR_MALFORMED_UTF8if the topic is not valid UTF-8

Example

char **topics;
int topic_count;
int i;

mosquitto_sub_topic_tokenise("$SYS/broker/uptime", &topics, &topic_count);

for(i=0; i<token_count; i++){
    printf("%d: %s\n", i, topics[i]);
}

See Also

mosquitto_sub_topic_tokens_free

mosquitto_sub_topic_tokens_free

libmosq_EXPORT int mosquitto_sub_topic_tokens_free(char ***topics,
int count)

Free memory that was allocated in mosquitto_sub_topic_tokenise.

Parameters

topicspointer to string array.
countcount of items in string array.

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif the input parameters were invalid.

See Also

mosquitto_sub_topic_tokenise

mosquitto_topic_matches_sub

libmosq_EXPORT int mosquitto_topic_matches_sub(const char *sub,
const char *topic,
bool *result)

Check whether a topic matches a subscription.

For example

foo/bar would match the subscription foo/# or +/bar non/matching would not match the subscription non/+/+

Parameters

subsubscription string to check topic against.
topictopic to check.
resultbool pointer to hold result.  Will be set to true if the topic matches the subscription.

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

mosquitto_topic_matches_sub2

libmosq_EXPORT int mosquitto_topic_matches_sub2(const char *sub,
size_t sublen,
const char *topic,
size_t topiclen,
bool *result)

Check whether a topic matches a subscription.

For example

foo/bar would match the subscription foo/# or +/bar non/matching would not match the subscription non/+/+

Parameters

subsubscription string to check topic against.
sublenlength in bytes of sub string
topictopic to check.
topiclenlength in bytes of topic string
resultbool pointer to hold result.  Will be set to true if the topic matches the subscription.

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif the input parameters were invalid.
MOSQ_ERR_NOMEMif an out of memory condition occurred.

mosquitto_pub_topic_check

libmosq_EXPORT int mosquitto_pub_topic_check(const char *topic)

Check whether a topic to be used for publishing is valid.

This searches for + or # in a topic and checks its length.

This check is already carried out in mosquitto_publish and mosquitto_will_set, there is no need to call it directly before them.  It may be useful if you wish to check the validity of a topic in advance of making a connection for example.

Parameters

topicthe topic to check

Returns

MOSQ_ERR_SUCCESSfor a valid topic
MOSQ_ERR_INVALif the topic contains a + or a #, or if it is too long.
MOSQ_ERR_MALFORMED_UTF8if sub or topic is not valid UTF-8

See Also

mosquitto_sub_topic_check

mosquitto_pub_topic_check2

libmosq_EXPORT int mosquitto_pub_topic_check2(const char *topic,
size_t topiclen)

Check whether a topic to be used for publishing is valid.

This searches for + or # in a topic and checks its length.

This check is already carried out in mosquitto_publish and mosquitto_will_set, there is no need to call it directly before them.  It may be useful if you wish to check the validity of a topic in advance of making a connection for example.

Parameters

topicthe topic to check
topiclenlength of the topic in bytes

Returns

MOSQ_ERR_SUCCESSfor a valid topic
MOSQ_ERR_INVALif the topic contains a + or a #, or if it is too long.
MOSQ_ERR_MALFORMED_UTF8if sub or topic is not valid UTF-8

See Also

mosquitto_sub_topic_check

mosquitto_sub_topic_check

libmosq_EXPORT int mosquitto_sub_topic_check(const char *topic)

Check whether a topic to be used for subscribing is valid.

This searches for + or # in a topic and checks that they aren’t in invalid positions, such as with foo/#/bar, foo/+bar or foo/bar#, and checks its length.

This check is already carried out in mosquitto_subscribe and mosquitto_unsubscribe, there is no need to call it directly before them.  It may be useful if you wish to check the validity of a topic in advance of making a connection for example.

Parameters

topicthe topic to check

Returns

MOSQ_ERR_SUCCESSfor a valid topic
MOSQ_ERR_INVALif the topic contains a + or a # that is in an invalid position, or if it is too long.
MOSQ_ERR_MALFORMED_UTF8if topic is not valid UTF-8

See Also

mosquitto_sub_topic_check

mosquitto_sub_topic_check2

libmosq_EXPORT int mosquitto_sub_topic_check2(const char *topic,
size_t topiclen)

Check whether a topic to be used for subscribing is valid.

This searches for + or # in a topic and checks that they aren’t in invalid positions, such as with foo/#/bar, foo/+bar or foo/bar#, and checks its length.

This check is already carried out in mosquitto_subscribe and mosquitto_unsubscribe, there is no need to call it directly before them.  It may be useful if you wish to check the validity of a topic in advance of making a connection for example.

Parameters

topicthe topic to check
topiclenthe length in bytes of the topic

Returns

MOSQ_ERR_SUCCESSfor a valid topic
MOSQ_ERR_INVALif the topic contains a + or a # that is in an invalid position, or if it is too long.
MOSQ_ERR_MALFORMED_UTF8if topic is not valid UTF-8

See Also

mosquitto_sub_topic_check

mosquitto_validate_utf8

libmosq_EXPORT int mosquitto_validate_utf8(const char *str,
int len)

Helper function to validate whether a UTF-8 string is valid, according to the UTF-8 spec and the MQTT additions.

Parameters

stra string to check
lenthe length of the string in bytes

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif str is NULL or len<0 or len>65536
MOSQ_ERR_MALFORMED_UTF8if str is not valid UTF-8

One line client helper functions

Summary
Functions
mosquitto_subscribe_simpleHelper function to make subscribing to a topic and retrieving some messages very straightforward.
mosquitto_subscribe_callbackHelper function to make subscribing to a topic and processing some messages very straightforward.

Functions

mosquitto_subscribe_simple

libmosq_EXPORT int mosquitto_subscribe_simple(
   struct mosquitto_message **messages,
   int msg_count,
   bool want_retained,
   const char *topic,
   int qos,
   const char *host,
   int port,
   const char *client_id,
   int keepalive,
   bool clean_session,
   const char *username,
   const char *password,
   const struct libmosquitto_will *will,
   const struct libmosquitto_tls *tls
)

Helper function to make subscribing to a topic and retrieving some messages very straightforward.

This connects to a broker, subscribes to a topic, waits for msg_count messages to be received, then returns after disconnecting cleanly.

Parameters

messagespointer to a “struct mosquitto_message *”.  The received messages will be returned here.  On error, this will be set to NULL.
msg_countthe number of messages to retrieve.
want_retainedif set to true, stale retained messages will be treated as normal messages with regards to msg_count.  If set to false, they will be ignored.
topicthe subscription topic to use (wildcards are allowed).
qosthe qos to use for the subscription.
hostthe broker to connect to.
portthe network port the broker is listening on.
client_idthe client id to use, or NULL if a random client id should be generated.
keepalivethe MQTT keepalive value.
clean_sessionthe MQTT clean session flag.
usernamethe username string, or NULL for no username authentication.
passwordthe password string, or NULL for an empty password.
willa libmosquitto_will struct containing will information, or NULL for no will.
tlsa libmosquitto_tls struct containing TLS related parameters, or NULL for no use of TLS.

Returns

MOSQ_ERR_SUCCESSon success
0 - on error.

mosquitto_subscribe_callback

libmosq_EXPORT int mosquitto_subscribe_callback(
   int (*callback)(struct mosquitto *, void *, const struct mosquitto_message *),
   void *userdata,
   const char *topic,
   int qos,
   const char *host,
   int port,
   const char *client_id,
   int keepalive,
   bool clean_session,
   const char *username,
   const char *password,
   const struct libmosquitto_will *will,
   const struct libmosquitto_tls *tls
)

Helper function to make subscribing to a topic and processing some messages very straightforward.

This connects to a broker, subscribes to a topic, then passes received messages to a user provided callback.  If the callback returns a 1, it then disconnects cleanly and returns.

Parameters

callbacka callback function in the following form: int callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message) Note that this is the same as the normal on_message callback, except that it returns an int.
userdatauser provided pointer that will be passed to the callback.
topicthe subscription topic to use (wildcards are allowed).
qosthe qos to use for the subscription.
hostthe broker to connect to.
portthe network port the broker is listening on.
client_idthe client id to use, or NULL if a random client id should be generated.
keepalivethe MQTT keepalive value.
clean_sessionthe MQTT clean session flag.
usernamethe username string, or NULL for no username authentication.
passwordthe password string, or NULL for an empty password.
willa libmosquitto_will struct containing will information, or NULL for no will.
tlsa libmosquitto_tls struct containing TLS related parameters, or NULL for no use of TLS.

Returns

MOSQ_ERR_SUCCESSon success
0 - on error.

Properties

Summary
Functions
mosquitto_property_add_byteAdd a new byte property to a property list.
mosquitto_property_add_int16Add a new int16 property to a property list.
mosquitto_property_add_int32Add a new int32 property to a property list.
mosquitto_property_add_varintAdd a new varint property to a property list.
mosquitto_property_add_binaryAdd a new binary property to a property list.
mosquitto_property_add_stringAdd a new string property to a property list.
mosquitto_property_add_string_pairAdd a new string pair property to a property list.
mosquitto_property_read_byteAttempt to read a byte property matching an identifier, from a property list or single property.
mosquitto_property_read_int16Read an int16 property value from a property.
mosquitto_property_read_int32Read an int32 property value from a property.
mosquitto_property_read_varintRead a varint property value from a property.
mosquitto_property_read_binaryRead a binary property value from a property.
mosquitto_property_read_stringRead a string property value from a property.
mosquitto_property_read_string_pairRead a string pair property value pair from a property.
mosquitto_property_free_allFree all properties from a list of properties.
mosquitto_property_copy_alldest : pointer for new property list src : property list
mosquitto_property_check_commandCheck whether a property identifier is valid for the given command.
mosquitto_property_check_allCheck whether a list of properties are valid for a particular command, whether there are duplicates, and whether the values are valid where possible.
mosquitto_string_to_property_infoParse a property name string and convert to a property identifier and data type.

Functions

mosquitto_property_add_byte

libmosq_EXPORT int mosquitto_property_add_byte(mosquitto_property **proplist,
int identifier,
uint8_t value)

Add a new byte property to a property list.

If *proplist == NULL, a new list will be created, otherwise the new property will be appended to the list.

Parameters

proplistpointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valueinteger value for the new property

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif identifier is invalid, or if proplist is NULL
MOSQ_ERR_NOMEMon out of memory

Example

mosquitto_property *proplist = NULL; mosquitto_property_add_byte(&proplist, MQTT_PROP_PAYLOAD_FORMAT_IDENTIFIER, 1);

mosquitto_property_add_int16

libmosq_EXPORT int mosquitto_property_add_int16(mosquitto_property **proplist,
int identifier,
uint16_t value)

Add a new int16 property to a property list.

If *proplist == NULL, a new list will be created, otherwise the new property will be appended to the list.

Parameters

proplistpointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_RECEIVE_MAXIMUM)
valueinteger value for the new property

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif identifier is invalid, or if proplist is NULL
MOSQ_ERR_NOMEMon out of memory

Example

mosquitto_property *proplist = NULL; mosquitto_property_add_int16(&proplist, MQTT_PROP_RECEIVE_MAXIMUM, 1000);

mosquitto_property_add_int32

libmosq_EXPORT int mosquitto_property_add_int32(mosquitto_property **proplist,
int identifier,
uint32_t value)

Add a new int32 property to a property list.

If *proplist == NULL, a new list will be created, otherwise the new property will be appended to the list.

Parameters

proplistpointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_MESSAGE_EXPIRY_INTERVAL)
valueinteger value for the new property

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif identifier is invalid, or if proplist is NULL
MOSQ_ERR_NOMEMon out of memory

Example

mosquitto_property *proplist = NULL; mosquitto_property_add_int32(&proplist, MQTT_PROP_MESSAGE_EXPIRY_INTERVAL, 86400);

mosquitto_property_add_varint

libmosq_EXPORT int mosquitto_property_add_varint(mosquitto_property **proplist,
int identifier,
uint32_t value)

Add a new varint property to a property list.

If *proplist == NULL, a new list will be created, otherwise the new property will be appended to the list.

Parameters

proplistpointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_SUBSCRIPTION_IDENTIFIER)
valueinteger value for the new property

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif identifier is invalid, or if proplist is NULL
MOSQ_ERR_NOMEMon out of memory

Example

mosquitto_property *proplist = NULL; mosquitto_property_add_varint(&proplist, MQTT_PROP_SUBSCRIPTION_IDENTIFIER, 1);

mosquitto_property_add_binary

libmosq_EXPORT int mosquitto_property_add_binary(mosquitto_property **proplist,
int identifier,
const void *value,
uint16_t len)

Add a new binary property to a property list.

If *proplist == NULL, a new list will be created, otherwise the new property will be appended to the list.

Parameters

proplistpointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valuepointer to the property data
lenlength of property data in bytes

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif identifier is invalid, or if proplist is NULL
MOSQ_ERR_NOMEMon out of memory

Example

mosquitto_property *proplist = NULL; mosquitto_property_add_binary(&proplist, MQTT_PROP_AUTHENTICATION_DATA, auth_data, auth_data_len);

mosquitto_property_add_string

libmosq_EXPORT int mosquitto_property_add_string(mosquitto_property **proplist,
int identifier,
const char *value)

Add a new string property to a property list.

If *proplist == NULL, a new list will be created, otherwise the new property will be appended to the list.

Parameters

proplistpointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_CONTENT_TYPE)
valuestring value for the new property, must be UTF-8 and zero terminated

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif identifier is invalid, if value is NULL, or if proplist is NULL
MOSQ_ERR_NOMEMon out of memory
MOSQ_ERR_MALFORMED_UTF8value is not valid UTF-8.

Example

mosquitto_property *proplist = NULL; mosquitto_property_add_string(&proplist, MQTT_PROP_CONTENT_TYPE, “application/json”);

mosquitto_property_add_string_pair

libmosq_EXPORT int mosquitto_property_add_string_pair(
   mosquitto_property **proplist,
   int identifier,
   const char *name,
   const char *value
)

Add a new string pair property to a property list.

If *proplist == NULL, a new list will be created, otherwise the new property will be appended to the list.

Parameters

proplistpointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_USER_PROPERTY)
namestring name for the new property, must be UTF-8 and zero terminated
valuestring value for the new property, must be UTF-8 and zero terminated

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif identifier is invalid, if name or value is NULL, or if proplist is NULL
MOSQ_ERR_NOMEMon out of memory
MOSQ_ERR_MALFORMED_UTF8if name or value are not valid UTF-8.

Example

mosquitto_property *proplist = NULL; mosquitto_property_add_string_pair(&proplist, MQTT_PROP_USER_PROPERTY, “client”, “mosquitto_pub”);

mosquitto_property_read_byte

libmosq_EXPORT const mosquitto_property *mosquitto_property_read_byte(
   const mosquitto_property *proplist,
   int identifier,
   uint8_t *value,
   bool skip_first
)

Attempt to read a byte property matching an identifier, from a property list or single property.  This function can search for multiple entries of the same identifier by using the returned value and skip_first.  Note however that it is forbidden for most properties to be duplicated.

If the property is not found, *value will not be modified, so it is safe to pass a variable with a default value to be potentially overwritten:

uint16_t keepalive = 60; // default value // Get value from property list, or keep default if not found. mosquitto_property_read_int16(proplist, MQTT_PROP_SERVER_KEEP_ALIVE, &keepalive, false);

Parameters

proplistmosquitto_property pointer, the list of properties or single property
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valuepointer to store the value, or NULL if the value is not required.
skip_firstboolean that indicates whether the first item in the list should be ignored or not.  Should usually be set to false.

Returns

A valid property pointer if the property is found NULL, if the property is not found, or proplist is NULL.

Example

// proplist is obtained from a callback mosquitto_property *prop; prop = mosquitto_property_read_byte(proplist, identifier, &value, false); while(prop){ printf(“value: %s\n”, value); prop = mosquitto_property_read_byte(prop, identifier, &value); }

mosquitto_property_read_int16

libmosq_EXPORT const mosquitto_property *mosquitto_property_read_int16(
   const mosquitto_property *proplist,
   int identifier,
   uint16_t *value,
   bool skip_first
)

Read an int16 property value from a property.

Parameters

propertyproperty to read
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valuepointer to store the value, or NULL if the value is not required.
skip_firstboolean that indicates whether the first item in the list should be ignored or not.  Should usually be set to false.

Returns

A valid property pointer if the property is found NULL, if the property is not found, or proplist is NULL.

Example

See mosquitto_property_read_byte

mosquitto_property_read_int32

libmosq_EXPORT const mosquitto_property *mosquitto_property_read_int32(
   const mosquitto_property *proplist,
   int identifier,
   uint32_t *value,
   bool skip_first
)

Read an int32 property value from a property.

Parameters

propertypointer to mosquitto_property pointer, the list of properties
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valuepointer to store the value, or NULL if the value is not required.
skip_firstboolean that indicates whether the first item in the list should be ignored or not.  Should usually be set to false.

Returns

A valid property pointer if the property is found NULL, if the property is not found, or proplist is NULL.

Example

See mosquitto_property_read_byte

mosquitto_property_read_varint

libmosq_EXPORT const mosquitto_property *mosquitto_property_read_varint(
   const mosquitto_property *proplist,
   int identifier,
   uint32_t *value,
   bool skip_first
)

Read a varint property value from a property.

Parameters

propertyproperty to read
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valuepointer to store the value, or NULL if the value is not required.
skip_firstboolean that indicates whether the first item in the list should be ignored or not.  Should usually be set to false.

Returns

A valid property pointer if the property is found NULL, if the property is not found, or proplist is NULL.

Example

See mosquitto_property_read_byte

mosquitto_property_read_binary

libmosq_EXPORT const mosquitto_property *mosquitto_property_read_binary(
   const mosquitto_property *proplist,
   int identifier,
   void **value,
   uint16_t *len,
   bool skip_first
)

Read a binary property value from a property.

On success, value must be free()’d by the application.

Parameters

propertyproperty to read
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valuepointer to store the value, or NULL if the value is not required.
skip_firstboolean that indicates whether the first item in the list should be ignored or not.  Should usually be set to false.

Returns

A valid property pointer if the property is found NULL, if the property is not found, or proplist is NULL, or if an out of memory condition occurred.

Example

See mosquitto_property_read_byte

mosquitto_property_read_string

libmosq_EXPORT const mosquitto_property *mosquitto_property_read_string(
   const mosquitto_property *proplist,
   int identifier,
   char **value,
   bool skip_first
)

Read a string property value from a property.

On success, value must be free()’d by the application.

Parameters

propertyproperty to read
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
valuepointer to char*, for the property data to be stored in, or NULL if the value is not required.
skip_firstboolean that indicates whether the first item in the list should be ignored or not.  Should usually be set to false.

Returns

A valid property pointer if the property is found NULL, if the property is not found, or proplist is NULL, or if an out of memory condition occurred.

Example

See mosquitto_property_read_byte

mosquitto_property_read_string_pair

libmosq_EXPORT const mosquitto_property *mosquitto_property_read_string_pair(
   const mosquitto_property *proplist,
   int identifier,
   char **name,
   char **value,
   bool skip_first
)

Read a string pair property value pair from a property.

On success, name and value must be free()’d by the application.

Parameters

propertyproperty to read
identifierproperty identifier (e.g.  MQTT_PROP_PAYLOAD_FORMAT_INDICATOR)
namepointer to char* for the name property data to be stored in, or NULL if the name is not required.
valuepointer to char*, for the property data to be stored in, or NULL if the value is not required.
skip_firstboolean that indicates whether the first item in the list should be ignored or not.  Should usually be set to false.

Returns

A valid property pointer if the property is found NULL, if the property is not found, or proplist is NULL, or if an out of memory condition occurred.

Example

See mosquitto_property_read_byte

mosquitto_property_free_all

libmosq_EXPORT void mosquitto_property_free_all(mosquitto_property **properties)

Free all properties from a list of properties.  Frees the list and sets *properties to NULL.

Parameters

propertieslist of properties to free

Example

mosquitto_properties *properties = NULL; // Add properties mosquitto_property_free_all(&properties);

mosquitto_property_copy_all

libmosq_EXPORT int mosquitto_property_copy_all(mosquitto_property **dest,
const mosquitto_property *src)

Parameters

dest : pointer for new property list src : property list

Returns

MOSQ_ERR_SUCCESSon successful copy
MOSQ_ERR_INVALif dest is NULL
MOSQ_ERR_NOMEMon out of memory (dest will be set to NULL)

mosquitto_property_check_command

libmosq_EXPORT int mosquitto_property_check_command(int command,
int identifier)

Check whether a property identifier is valid for the given command.

Parameters

commandMQTT command (e.g.  CMD_CONNECT)
identifierMQTT property (e.g.  MQTT_PROP_USER_PROPERTY)

Returns

MOSQ_ERR_SUCCESSif the identifier is valid for command
MOSQ_ERR_PROTOCOLif the identifier is not valid for use with command.

mosquitto_property_check_all

libmosq_EXPORT int mosquitto_property_check_all(
   int command,
   const mosquitto_property *properties
)

Check whether a list of properties are valid for a particular command, whether there are duplicates, and whether the values are valid where possible.

Note that this function is used internally in the library whenever properties are passed to it, so in basic use this is not needed, but should be helpful to check property lists before the point of using them.

Parameters

commandMQTT command (e.g.  CMD_CONNECT)
propertieslist of MQTT properties to check.

Returns

MOSQ_ERR_SUCCESSif all properties are valid
MOSQ_ERR_DUPLICATE_PROPERTYif a property is duplicated where it is forbidden.
MOSQ_ERR_PROTOCOLif any property is invalid

mosquitto_string_to_property_info

libmosq_EXPORT int mosquitto_string_to_property_info(const char *propname,
int *identifier,
int *type)

Parse a property name string and convert to a property identifier and data type.  The property name is as defined in the MQTT specification, with - as a separator, for example: payload-format-indicator.

Parameters

propnamethe string to parse
identifierpointer to an int to receive the property identifier
typepointer to an int to receive the property type

Returns

MOSQ_ERR_SUCCESSon success
MOSQ_ERR_INVALif the string does not match a property

Example

mosquitto_string_to_property_info(“response-topic”, &id, &type); // id == MQTT_PROP_RESPONSE_TOPIC // type == MQTT_PROP_TYPE_STRING

libmosq_EXPORT int mosquitto_lib_init(void)
Must be called before any other mosquitto functions.
libmosq_EXPORT int mosquitto_lib_version(int *major,
int *minor,
int *revision)
Can be used to obtain version information for the mosquitto library.
libmosq_EXPORT int mosquitto_lib_cleanup(void)
Call to free resources associated with the library.
libmosq_EXPORT struct mosquitto *mosquitto_new(const char *id,
bool clean_session,
void *obj)
Create a new mosquitto client instance.
libmosq_EXPORT void mosquitto_destroy(struct mosquitto *mosq)
Use to free memory associated with a mosquitto client instance.
libmosq_EXPORT int mosquitto_reinitialise(struct mosquitto *mosq,
const char *id,
bool clean_session,
void *obj)
This function allows an existing mosquitto client to be reused.
libmosq_EXPORT int mosquitto_will_set(struct mosquitto *mosq,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain)
Configure will information for a mosquitto instance.
libmosq_EXPORT int mosquitto_will_set_v5(struct mosquitto *mosq,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain,
mosquitto_property *properties)
Configure will information for a mosquitto instance, with attached properties.
libmosq_EXPORT int mosquitto_will_clear(struct mosquitto *mosq)
Remove a previously configured will.
libmosq_EXPORT int mosquitto_username_pw_set(struct mosquitto *mosq,
const char *username,
const char *password)
Configure username and password for a mosquitto instance.
libmosq_EXPORT int mosquitto_connect(struct mosquitto *mosq,
const char *host,
int port,
int keepalive)
Connect to an MQTT broker.
libmosq_EXPORT int mosquitto_connect_bind(struct mosquitto *mosq,
const char *host,
int port,
int keepalive,
const char *bind_address)
Connect to an MQTT broker.
libmosq_EXPORT int mosquitto_connect_bind_v5(
   struct mosquitto *mosq,
   const char *host,
   int port,
   int keepalive,
   const char *bind_address,
   const mosquitto_property *properties
)
Connect to an MQTT broker.
libmosq_EXPORT int mosquitto_connect_async(struct mosquitto *mosq,
const char *host,
int port,
int keepalive)
Connect to an MQTT broker.
libmosq_EXPORT int mosquitto_connect_bind_async(struct mosquitto *mosq,
const char *host,
int port,
int keepalive,
const char *bind_address)
Connect to an MQTT broker.
libmosq_EXPORT int mosquitto_connect_srv(struct mosquitto *mosq,
const char *host,
int keepalive,
const char *bind_address)
Connect to an MQTT broker.
libmosq_EXPORT int mosquitto_reconnect(struct mosquitto *mosq)
Reconnect to a broker.
libmosq_EXPORT int mosquitto_reconnect_async(struct mosquitto *mosq)
Reconnect to a broker.
libmosq_EXPORT int mosquitto_disconnect(struct mosquitto *mosq)
Disconnect from the broker.
libmosq_EXPORT int mosquitto_disconnect_v5(
   struct mosquitto *mosq,
   int reason_code,
   const mosquitto_property *properties
)
Disconnect from the broker, with attached MQTT properties.
libmosq_EXPORT int mosquitto_publish(struct mosquitto *mosq,
int *mid,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain)
Publish a message on a given topic.
libmosq_EXPORT int mosquitto_publish_v5(struct mosquitto *mosq,
int *mid,
const char *topic,
int payloadlen,
const void *payload,
int qos,
bool retain,
const mosquitto_property *properties)
Publish a message on a given topic, with attached MQTT properties.
libmosq_EXPORT int mosquitto_subscribe(struct mosquitto *mosq,
int *mid,
const char *sub,
int qos)
Subscribe to a topic.
libmosq_EXPORT int mosquitto_subscribe_v5(struct mosquitto *mosq,
int *mid,
const char *sub,
int qos,
int options,
const mosquitto_property *properties)
Subscribe to a topic, with attached MQTT properties.
libmosq_EXPORT int mosquitto_subscribe_multiple(
   struct mosquitto *mosq,
   int *mid,
   int sub_count,
   char *const *const sub,
   int qos,
   int options,
   const mosquitto_property *properties
)
Subscribe to multiple topics.
libmosq_EXPORT int mosquitto_unsubscribe(struct mosquitto *mosq,
int *mid,
const char *sub)
Unsubscribe from a topic.
libmosq_EXPORT int mosquitto_unsubscribe_v5(
   struct mosquitto *mosq,
   int *mid,
   const char *sub,
   const mosquitto_property *properties
)
Unsubscribe from a topic, with attached MQTT properties.
libmosq_EXPORT int mosquitto_unsubscribe_multiple(
   struct mosquitto *mosq,
   int *mid,
   int sub_count,
   char *const *const sub,
   const mosquitto_property *properties
)
Unsubscribe from multiple topics.
libmosq_EXPORT int mosquitto_message_copy(struct mosquitto_message *dst,
const struct mosquitto_message *src)
Copy the contents of a mosquitto message to another message.
libmosq_EXPORT void mosquitto_message_free(struct mosquitto_message **message)
Completely free a mosquitto_message struct.
libmosq_EXPORT void mosquitto_message_free_contents(
   struct mosquitto_message *message
)
Free a mosquitto_message struct contents, leaving the struct unaffected.
libmosq_EXPORT int mosquitto_loop_forever(struct mosquitto *mosq,
int timeout,
int max_packets)
This function call loop() for you in an infinite blocking loop.
libmosq_EXPORT int mosquitto_loop_start(struct mosquitto *mosq)
This is part of the threaded client interface.
libmosq_EXPORT int mosquitto_loop_stop(struct mosquitto *mosq,
bool force)
This is part of the threaded client interface.
libmosq_EXPORT int mosquitto_loop(struct mosquitto *mosq,
int timeout,
int max_packets)
The main network loop for the client.
libmosq_EXPORT int mosquitto_loop_read(struct mosquitto *mosq,
int max_packets)
Carry out network read operations.
libmosq_EXPORT int mosquitto_loop_write(struct mosquitto *mosq,
int max_packets)
Carry out network write operations.
libmosq_EXPORT int mosquitto_loop_misc(struct mosquitto *mosq)
Carry out miscellaneous operations required as part of the network loop.
libmosq_EXPORT int mosquitto_socket(struct mosquitto *mosq)
Return the socket handle for a mosquitto instance.
libmosq_EXPORT bool mosquitto_want_write(struct mosquitto *mosq)
Returns true if there is data ready to be written on the socket.
libmosq_EXPORT int mosquitto_threaded_set(struct mosquitto *mosq,
bool threaded)
Used to tell the library that your application is using threads, but not using mosquitto_loop_start.
libmosq_EXPORT int mosquitto_opts_set(struct mosquitto *mosq,
enum mosq_opt_t option,
void *value)
Used to set options for the client.
libmosq_EXPORT int mosquitto_int_option(struct mosquitto *mosq,
enum mosq_opt_t option,
int value)
Used to set integer options for the client.
libmosq_EXPORT int mosquitto_void_option(struct mosquitto *mosq,
enum mosq_opt_t option,
void *value)
Used to set void* options for the client.
libmosq_EXPORT int mosquitto_reconnect_delay_set(
   struct mosquitto *mosq,
   unsigned int reconnect_delay,
   unsigned int reconnect_delay_max,
   bool reconnect_exponential_backoff
)
Control the behaviour of the client when it has unexpectedly disconnected in mosquitto_loop_forever or after mosquitto_loop_start.
libmosq_EXPORT int mosquitto_max_inflight_messages_set(
   struct mosquitto *mosq,
   unsigned int max_inflight_messages
)
This function is deprected.
libmosq_EXPORT void mosquitto_message_retry_set(struct mosquitto *mosq,
unsigned int message_retry)
This function now has no effect.
libmosq_EXPORT void mosquitto_user_data_set(struct mosquitto *mosq,
void *obj)
When mosquitto_new is called, the pointer given as the “obj” parameter will be passed to the callbacks as user data.
libmosq_EXPORT void *mosquitto_userdata(struct mosquitto *mosq)
Retrieve the “userdata” variable for a mosquitto client.
libmosq_EXPORT int mosquitto_tls_set(
   struct mosquitto *mosq,
   const char *cafile,
   const char *capath,
   const char *certfile,
   const char *keyfile,
   int (*pw_callback)(char *buf, int size, int rwflag, void *userdata)
)
Configure the client for certificate based SSL/TLS support.
libmosq_EXPORT int mosquitto_tls_insecure_set(struct mosquitto *mosq,
bool value)
Configure verification of the server hostname in the server certificate.
libmosq_EXPORT int mosquitto_tls_opts_set(struct mosquitto *mosq,
int cert_reqs,
const char *tls_version,
const char *ciphers)
Set advanced SSL/TLS options.
libmosq_EXPORT int mosquitto_tls_psk_set(struct mosquitto *mosq,
const char *psk,
const char *identity,
const char *ciphers)
Configure the client for pre-shared-key based TLS support.
libmosq_EXPORT void mosquitto_connect_callback_set(
   struct mosquitto *mosq,
   void (*on_connect)(struct mosquitto *, void *, int)
)
Set the connect callback.
libmosq_EXPORT void mosquitto_connect_with_flags_callback_set(
   struct mosquitto *mosq,
   void (*on_connect)(struct mosquitto *, void *, int, int)
)
Set the connect callback.
libmosq_EXPORT void mosquitto_connect_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_connect)(struct mosquitto *, void *, int, int, const mosquitto_property *props)
)
Set the connect callback.
libmosq_EXPORT void mosquitto_disconnect_callback_set(
   struct mosquitto *mosq,
   void (*on_disconnect)(struct mosquitto *, void *, int)
)
Set the disconnect callback.
libmosq_EXPORT void mosquitto_disconnect_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_disconnect)(struct mosquitto *, void *, int, const mosquitto_property *)
)
Set the disconnect callback.
libmosq_EXPORT void mosquitto_publish_callback_set(
   struct mosquitto *mosq,
   void (*on_publish)(struct mosquitto *, void *, int)
)
Set the publish callback.
libmosq_EXPORT void mosquitto_publish_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_publish)(struct mosquitto *, void *, int, int, const mosquitto_property *)
)
Set the publish callback.
libmosq_EXPORT void mosquitto_message_callback_set(
   struct mosquitto *mosq,
   void (*on_message)(struct mosquitto *, void *, const struct mosquitto_message *)
)
Set the message callback.
libmosq_EXPORT void mosquitto_message_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_message)(struct mosquitto *, void *, const struct mosquitto_message *, const mosquitto_property *)
)
Set the message callback.
libmosq_EXPORT void mosquitto_subscribe_callback_set(
   struct mosquitto *mosq,
   void (*on_subscribe)(struct mosquitto *, void *, int, int, const int *)
)
Set the subscribe callback.
libmosq_EXPORT void mosquitto_subscribe_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_subscribe)(struct mosquitto *, void *, int, int, const int *, const mosquitto_property *)
)
Set the subscribe callback.
libmosq_EXPORT void mosquitto_unsubscribe_callback_set(
   struct mosquitto *mosq,
   void (*on_unsubscribe)(struct mosquitto *, void *, int)
)
Set the unsubscribe callback.
libmosq_EXPORT void mosquitto_unsubscribe_v5_callback_set(
   struct mosquitto *mosq,
   void (*on_unsubscribe)(struct mosquitto *, void *, int, const mosquitto_property *)
)
Set the unsubscribe callback.
libmosq_EXPORT void mosquitto_log_callback_set(
   struct mosquitto *mosq,
   void (*on_log)(struct mosquitto *, void *, int, const char *)
)
Set the logging callback.
libmosq_EXPORT int mosquitto_string_option(struct mosquitto *mosq,
enum mosq_opt_t option,
const char *value)
Used to set const char* options for the client.
libmosq_EXPORT int mosquitto_socks5_set(struct mosquitto *mosq,
const char *host,
int port,
const char *username,
const char *password)
Configure the client to use a SOCKS5 proxy when connecting.
libmosq_EXPORT const char *mosquitto_strerror(int mosq_errno)
Call to obtain a const string description of a mosquitto error number.
libmosq_EXPORT const char *mosquitto_connack_string(int connack_code)
Call to obtain a const string description of an MQTT connection result.
libmosq_EXPORT const char *mosquitto_reason_string(int reason_code)
Call to obtain a const string description of an MQTT reason code.
libmosq_EXPORT int mosquitto_string_to_command(const char *str,
int *cmd)
Take a string input representing an MQTT command and convert it to the libmosquitto integer representation.
libmosq_EXPORT int mosquitto_sub_topic_tokenise(const char *subtopic,
char ***topics,
int *count)
Tokenise a topic or subscription string into an array of strings representing the topic hierarchy.
libmosq_EXPORT int mosquitto_sub_topic_tokens_free(char ***topics,
int count)
Free memory that was allocated in mosquitto_sub_topic_tokenise.
libmosq_EXPORT int mosquitto_topic_matches_sub(const char *sub,
const char *topic,
bool *result)
Check whether a topic matches a subscription.
libmosq_EXPORT int mosquitto_topic_matches_sub2(const char *sub,
size_t sublen,
const char *topic,
size_t topiclen,
bool *result)
Check whether a topic matches a subscription.
libmosq_EXPORT int mosquitto_pub_topic_check(const char *topic)
Check whether a topic to be used for publishing is valid.
libmosq_EXPORT int mosquitto_pub_topic_check2(const char *topic,
size_t topiclen)
Check whether a topic to be used for publishing is valid.
libmosq_EXPORT int mosquitto_sub_topic_check(const char *topic)
Check whether a topic to be used for subscribing is valid.
libmosq_EXPORT int mosquitto_sub_topic_check2(const char *topic,
size_t topiclen)
Check whether a topic to be used for subscribing is valid.
libmosq_EXPORT int mosquitto_validate_utf8(const char *str,
int len)
Helper function to validate whether a UTF-8 string is valid, according to the UTF-8 spec and the MQTT additions.
libmosq_EXPORT int mosquitto_subscribe_simple(
   struct mosquitto_message **messages,
   int msg_count,
   bool want_retained,
   const char *topic,
   int qos,
   const char *host,
   int port,
   const char *client_id,
   int keepalive,
   bool clean_session,
   const char *username,
   const char *password,
   const struct libmosquitto_will *will,
   const struct libmosquitto_tls *tls
)
Helper function to make subscribing to a topic and retrieving some messages very straightforward.
libmosq_EXPORT int mosquitto_subscribe_callback(
   int (*callback)(struct mosquitto *, void *, const struct mosquitto_message *),
   void *userdata,
   const char *topic,
   int qos,
   const char *host,
   int port,
   const char *client_id,
   int keepalive,
   bool clean_session,
   const char *username,
   const char *password,
   const struct libmosquitto_will *will,
   const struct libmosquitto_tls *tls
)
Helper function to make subscribing to a topic and processing some messages very straightforward.
libmosq_EXPORT int mosquitto_property_add_byte(mosquitto_property **proplist,
int identifier,
uint8_t value)
Add a new byte property to a property list.
libmosq_EXPORT int mosquitto_property_add_int16(mosquitto_property **proplist,
int identifier,
uint16_t value)
Add a new int16 property to a property list.
libmosq_EXPORT int mosquitto_property_add_int32(mosquitto_property **proplist,
int identifier,
uint32_t value)
Add a new int32 property to a property list.
libmosq_EXPORT int mosquitto_property_add_varint(mosquitto_property **proplist,
int identifier,
uint32_t value)
Add a new varint property to a property list.
libmosq_EXPORT int mosquitto_property_add_binary(mosquitto_property **proplist,
int identifier,
const void *value,
uint16_t len)
Add a new binary property to a property list.
libmosq_EXPORT int mosquitto_property_add_string(mosquitto_property **proplist,
int identifier,
const char *value)
Add a new string property to a property list.
libmosq_EXPORT int mosquitto_property_add_string_pair(
   mosquitto_property **proplist,
   int identifier,
   const char *name,
   const char *value
)
Add a new string pair property to a property list.
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_byte(
   const mosquitto_property *proplist,
   int identifier,
   uint8_t *value,
   bool skip_first
)
Attempt to read a byte property matching an identifier, from a property list or single property.
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_int16(
   const mosquitto_property *proplist,
   int identifier,
   uint16_t *value,
   bool skip_first
)
Read an int16 property value from a property.
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_int32(
   const mosquitto_property *proplist,
   int identifier,
   uint32_t *value,
   bool skip_first
)
Read an int32 property value from a property.
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_varint(
   const mosquitto_property *proplist,
   int identifier,
   uint32_t *value,
   bool skip_first
)
Read a varint property value from a property.
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_binary(
   const mosquitto_property *proplist,
   int identifier,
   void **value,
   uint16_t *len,
   bool skip_first
)
Read a binary property value from a property.
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_string(
   const mosquitto_property *proplist,
   int identifier,
   char **value,
   bool skip_first
)
Read a string property value from a property.
libmosq_EXPORT const mosquitto_property *mosquitto_property_read_string_pair(
   const mosquitto_property *proplist,
   int identifier,
   char **name,
   char **value,
   bool skip_first
)
Read a string pair property value pair from a property.
libmosq_EXPORT void mosquitto_property_free_all(mosquitto_property **properties)
Free all properties from a list of properties.
libmosq_EXPORT int mosquitto_property_copy_all(mosquitto_property **dest,
const mosquitto_property *src)
dest : pointer for new property list src : property list
libmosq_EXPORT int mosquitto_property_check_command(int command,
int identifier)
Check whether a property identifier is valid for the given command.
libmosq_EXPORT int mosquitto_property_check_all(
   int command,
   const mosquitto_property *properties
)
Check whether a list of properties are valid for a particular command, whether there are duplicates, and whether the values are valid where possible.
libmosq_EXPORT int mosquitto_string_to_property_info(const char *propname,
int *identifier,
int *type)
Parse a property name string and convert to a property identifier and data type.
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