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 [mosquitto-mqtt5-test1.tar.gz]: https://mosquitto.org/files/source/test/mosquitto-mqtt5-test1.tar.gz