MQTT 2.4 documentation

Development Documentation
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The following options all work:

Option 1 configure Broker as a bridge and items as things “under” that bridge.

Things file looks like:

Bridge mqtt:broker:WorkBroker "Work Broker" [ host="localhost", port="1883", secure=false, username="openhabian", password="ohmqtt", clientID="WORKOPENHAB24" ]
{
    Thing topic WorkSonoff "Work Sonoff" @ "Home" {
    Channels:
        Type switch : WorkLight "Work Light" [ stateTopic="stat/christmas3/POWER", commandTopic="cmnd/christmas3/POWER" ]
        Type switch : WorkLightTele "Work Tele" [ stateTopic="tele/christmas3/STATE", transformationPattern="JSONPATH:$.POWER" ]
    }
}

Option 2 configure Broker as a “thing” and generic other MQTT stuff as things.

Things file looks like:

Thing mqtt:broker:WorkBroker "Work Broker" [ host="localhost", port="1883", secure=false, username="openhabian", password="ohmqtt", clientID="WORKOPENHAB24" ]

Thing mqtt:topic:WorkBroker:WorkSonoff "Work Sonoff" (mqtt:broker:WorkBroker) @ "Home" {
    Channels:
        Type switch : WorkLight "Work Light" [ stateTopic="stat/christmas3/POWER", commandTopic="cmnd/christmas3/POWER" ]
        Type switch : WorkLightTele "Work Tele" [ stateTopic="tele/christmas3/STATE", transformationPattern="JSONPATH:$.POWER" ]
}

Option 3 same as option 2 - but broker is called “Bridge” instead of “Thing”

Things file looks like:

Bridge mqtt:broker:WorkBroker "Work Broker" [ host="localhost", port="1883", secure=false, username="openhabian", password="ohmqtt", clientID="WORKOPENHAB24" ]

Thing mqtt:topic:WorkBroker:WorkSonoff "Work Sonoff" (mqtt:broker:WorkBroker) @ "Home" {
    Channels:
        Type switch : WorkLight "Work Light" [ stateTopic="stat/christmas3/POWER", commandTopic="cmnd/christmas3/POWER" ]
        Type switch : WorkLightTele "Work Tele" [ stateTopic="tele/christmas3/STATE", transformationPattern="JSONPATH:$.POWER" ]
}

I’m beginning to see where the confusion comes from in the docs - everything depends on those { } after the bridge configuration. Surprisingly - the .items file that works with all of these is the same. It looks like:

Switch SW_WorkLight "Work Light Switch" { channel="mqtt:topic:WorkBroker:WorkSonoff:WorkLight", channel="mqtt:topic:WorkBroker:WorkSonoff:WorkLightTele" }

Interestingly - it doesn’t seem to matter between option 2 and 3 whether I type “bridge”, “thing”, or just nothing at all (start the line with mqtt:broker:...) - the broker connection is still working properly. The documentation for the MQTT 2.4 broker indeed shows it without bridge or thing, just starting mqtt:broker:...

I prefer Option 1 and plan to set up my system as such. I also see the benefit in the other approach (let’s call it non-bridged) if someone has many MQTT things in their house and would like to keep them separated into separate files but under the same broker. I think next I will put together a PR for the documentation showing these configuration options…

Does anyone have an example about what things look like with a functioning broker configured in paper ui with things and items files for defining their various channels?

Edit: new PR here.

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