|Re: [paho-dev] MQTT 3.1.1 support for Paho clients|
I would be quite happy with that direction. I do like the idea of trying 3.1.1 first and then retrying with 3.1 if it fails (with a CONNACK... do you retry even if you don't get a CONNACK? Not sure about that.) with an option to try with 3.1 first (must have that....).
I don't want to break existing applications (at least for 6 to 12 months :-) . This means that 3.1 must be the default for now if we don't automatically fall back. And yes, having a new major version of the clients could enable us to switch the default.
If we do automatically fall back, then having 3.1.1 as the default is the obvious choice, as most, if not all servers will support 3.1 as well as 3.1.1. If you try 3.1 first you will be stuck with that. The downside is an extra connect cycle.
I prefer the option "try 3.1.1 first and automatically try 3.1 under the covers if that fails". Then applications don't have to change, and they can connect easily to either 3.1 or 3.1.1 servers (assuming other differences in the protocol versions are minimal). And as I said we can have a connect option to turn off automatic fall back if you don't want it.
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