A protocol isn’t much use without a specification that allows others to understand how it works and how they can implement it. This has been a missing piece to the MQTT story for a while. The specification was originally made available as a part of the WebSphere Message Broker InfoCenter. This was done to get the protocol ‘out there’ with the intent that others could adopt it, but it came with the InfoCenter license that didn’t allow for others to implement it. With MQTT support moving from Message Broker to MQ, the protocol needed a new home.
One week ahead of the planned availability date of MQTT support in MQ, the MQTT v3.1 specification has been published on IBM developerWorks. This has been done with a royalty free license so anyone is free to create their own implementations.
You may notice the version has bumped to v3.1. There are some updates to the spec that adds support for security and clarifies the use of UTF-8 versus US-ASCII. The spec has also had a rewrite to make it a clearer and more complete document.