This article introduces the MQTT protocol and its advantages, and demonstrates the use of MQTT in Elixir.

User Properties are the user-defined properties that allow users to add their metadata to MQTT messages to expand more application scenarios.

MQTT 5.0 adds a new feature enhanced authentication, which includes query/response style authentication can implement bi-directional authentication of the client and broker.

MQTT 5.0 brings many new features, this article will give an introduction to the use of the new feature "flow control" in an easy-to-understand way.

Compared with MQTT 3.1.1, MQTT 5.0 protocol adds many properties, which are distributed in variable headers and payloads of packet.