There are a number of mailing lists and discussion groups and spaces for MQTT now, so I thought it might be useful to quickly summarise the main ones – and clarify what they are for.

• MQTT on Google Groups – this is mostly where discussion of the protocol itself happen, along with the broader ecosystem of implementations and use cases. Much of what is discussed in the Google Group is used to clarify the specification and improve the wiki.
• mosquitto-users on Launchpad (formerly mqtt-users) - owned by the mosquitto project, so this is primarily for discussion of issues and questions around the mosquitto broker.
• paho-dev Eclipse list – for implementation specifics on Eclipse Paho code (the new home of the “reference” C and Java clients) and future requirements.
• m2m-iwg Eclipse list – Machine-to-Machine Industry Working Group topics ie those spanning Eclipse Paho and Eclipse Koneki. The goal is to avoid too many project-specific discussions here but to look at the broader initiatives of the IWG.

Users of all of the lists are generally very friendly and can help you to navigate between them, but I just thought it would be useful to explain the “main purpose” of each group. Discussions are not limited to mailing lists and happen on Twitter, in IRC, and across the web. We try to follow as many of them as possible! There’s an additional list on the Community page.

For more about MQTT and the relationship to Eclipse, check our wiki page MQTT at Eclipse. For more on mosquitto, check out that project’s excellent website!