The work on MQTT v5 support in Mosquitto has reached a point where it may be of interest to a range of people. It is not yet complete, but wider testing and feedback would be appreciated.

The source is available at mosquitto-mqtt5-test1.tar.gz and can be compiled as normal.

Supported features

  • Session expiry
  • Message expiry
  • Reason code on all ACKs (not all reason codes are used)
  • Reason string on all ACKs (no reason strings are provided by the broker however)
  • Payload format and content type
  • Request / response pattern
  • Subscription ID
  • Topic alias
  • Flow control
  • User properties
  • Optional server feature availability
  • Subscription options
  • Server keep alive
  • Assigned Client ID

Unsupported features

  • Shared subscriptions
  • Extended authentication
  • Server reference
  • Not all reason codes are used by the broker
  • Bridges do not use MQTT v5
  • On disk persistence does not include MQTT 5 property support
  • The broker will not create topic aliases