mosquitto_sub — an MQTT version 3.1 client for subscribing to topics
mosquitto_sub [-c] [-d] [-h hostname] [-i client_id] [-I client id prefix] [-k keepalive time] [-p port number] [-q message QoS] [--quiet] [-v] [
[-u username]
[-P password]
] [
--will-topic topic
[--will-payload payload]
[--will-qos qos]
[--will-retain]
] [[
{ --cafile file | --capath dir }
[--cert file]
[--key file]
] | [
--psk hex-key
--psk-identity identity
]] -t message-topic...
mosquitto_sub [--help]
mosquitto_sub is a simple MQTT version 3.1 client that will subscribe to a topic and print the messages that it receives.
-c, --disable-clean-sessionDisable the 'clean session' flag. This means that all of the subscriptions for the client will be maintained after it disconnects, along with subsequent QoS 1 and QoS 2 messages that arrive. When the client reconnects, it will receive all of the queued messages.
If using this option, it is recommended that the
client id is set manually with --id
--cafileDefine the path to a file containing PEM encoded CA certificates that are trusted. Used to enable SSL communication.
See also --capath
--capathDefine the path to a directory containing PEM encoded CA certificates that are trusted. Used to enable SSL communication.
For --capath to work correctly, the
certificate files must have ".crt" as the file ending
and you must run "c_rehash <path to capath>" each
time you add/remove a certificate.
See also --cafile
--certDefine the path to a file containing a PEM encoded certificate for this client, if required by the server.
See also --key.
-d, --debugEnable debug messages.
--helpDisplay usage information.
-h, --hostSpecify the host to connect to. Defaults to localhost.
-i, --idThe id to use for this client. If not given, defaults
to mosquitto_sub_ appended with the process id of the
client. Cannot be used at the same time as the
--id-prefix argument.
-I, --id-prefixProvide a prefix that the client id will be built
from by appending the process id of the client. This is
useful where the broker is using the clientid_prefixes
option. Cannot be used at the same time as the
--id argument.
-k, --keepaliveThe number of seconds between sending PING commands to the broker for the purposes of informing it we are still connected and functioning. Defaults to 60 seconds.
--keyDefine the path to a file containing a PEM encoded private key for this client, if required by the server.
See also --cert.
-p, --portConnect to the port specified instead of the default 1883.
-P, --pwProvide a password to be used for authenticating with
the broker. Using this argument without also specifying a
username is invalid. This requires a broker that supports
MQTT v3.1. See also the --username option.
--pskProvide the hexadecimal (no leading 0x)
pre-shared-key matching the one used on the broker to
use TLS-PSK encryption support.
--psk-identity must also be provided
to enable TLS-PSK.
--psk-identityThe client identity to use with TLS-PSK support. This may be used instead of a username if the broker is configured to do so.
-q, --qosSpecify the quality of service desired for the incoming messages, from 0, 1 and 2. Defaults to 0. See mqtt(7) for more information on QoS.
The QoS is identical for all topics subscribed to in a single instance of mosquitto_sub.
--quietIf this argument is given, no runtime errors will be
printed. This excludes any error messages given in case of
invalid user input (e.g. using --port without a
port).
-t, --topicThe MQTT topic to subscribe to. See mqtt(7) for more information on MQTT topics.
This option may be repeated to subscribe to multiple topics.
-u, --usernameProvide a username to be used for authenticating with
the broker. This requires a broker that supports MQTT v3.1.
See also the --pw argument.
-v, --verbosePrint received messages verbosely. With this argument, messages will be printed as "topic payload". When this argument is not given, the messages are printed as "payload".
--will-payloadSpecify a message that will be stored by the broker
and sent out if this client disconnects unexpectedly. This
must be used in conjunction with --will-topic.
--will-qosThe QoS to use for the Will. Defaults to 0. This must
be used in conjunction with --will-topic.
--will-retainIf given, if the client disconnects unexpectedly the
message sent out will be treated as a retained message.
This must be used in conjunction with --will-topic.
--will-topicThe topic on which to send a Will, in the event that the client disconnects unexpectedly.
mosquitto_sub can register a message with the broker that will be sent out if it disconnects unexpectedly. See mqtt(7) for more information.
The minimum requirement for this is to use --will-topic to
specify which topic the will should be sent out on. This will result in
a non-retained, zero length message with QoS 0.
Use the --will-retain, --will-payload and --will-qos arguments to
modify the other will parameters.
Note that these really are examples - the subscriptions will work if you run them as shown, but there must be something publishing messages on those topics for you to receive anything.
Subscribe to temperature information on localhost with QoS 1:
mosquitto_sub -t sensors/temperature -q 1
Subscribe to hard drive temperature updates on multiple machines/hard drives. This expects each machine to be publishing its hard drive temperature to sensors/machines/HOSTNAME/temperature/HD_NAME.
mosquitto_sub -t sensors/machines/+/temperature/+
Subscribe to all broker status messages:
mosquitto_sub -v -t \$SYS/#