What MQTT Versions Does Ignition Support?

The MQTT Modules for Ignition are all Sparkplug compatible. Sparkplug will work with both MQTT 3.1.1 and MQTT 5.0. We’re in the process of calling out the specific portions of the MQTT protocol that are required via the Sparkplug Working Group. This is because Sparkplug doesn’t use things like persistent sessions or QoS2.

I should note that many cloud based MQTT Servers such as AWS IoT Core and Azure IoT Hubs are not compliant with the MQTT specification and will not work with the MQTT Modules for Ignition. Some MQTT Servers I know will work include MQTT Distributor for Ignition, Cirrus Link’s Chariot MQTT Server, and HiveMQ.