OK - here’s a little treat for all the historians out there ;)
Here is the original MQTT v2.0 specification document, complete with discussion comments about aspects of the protocol.
As Arlen noted, MQTT has been through a few name changes in its history: OTWP, MQISDP, MQIPDP, MQTT!
(for the curious: On The Wire Protocol, Message Queuing Integrator - SCADA Device Protocol, Message Queuing Integrator - Pervasive Device Protocol, and Message Queuing Telemetry Transport)
It is now just called “MQTT”, i.e. it doesn’t stand for anything, that’s just its name.
And here is the original v3.0 specification, which is the first one that was properly published, i.e. formally placed in the public domain.
Note that v1.0 was not published - it was a working version between Arlen and me, and we had the first - Marconi style - publication from Kansas City US to Isle of Wight UK using that protocol in April 1999.
I’d spent a week writing up the specification document, finished on the friday lunchtime, and spent the afternoon writing a perl implementation of it. Arlen had the same idea, and wrote an embedded C client.
Oops, then we realised we had both written a client, and we had no broker to publish to!
So I spent the next week writing a perl broker, so we could publish and subscribe to each other! The first edit of that is dated 12-Apr-99.
<sigh> #nostalgia
Andy