I personally have found the following blog posts extremely helpful in learning about MQTT: https://www.hivemq.com/tags/mqtt-essentials/ https://www.hivemq.com/t

I personally have found the following blog posts extremely helpful in learning about MQTT: https://www.hivemq.com/tags/mqtt-essentials/ https://www.hivemq.com/tags/mqtt-essentials/ Also, the spec is actually pretty readable: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-o... Note: I'm not affiliated with HiveMQ.