MQTT problems. (nodes, messages and python)

General
1

(How has to become this complicated?)

I have a python script running and I added this line:
client.publish("alarm_clock/oops",text)

I then have an MQTT IN node and set it so:

[{"id":"20f5e9bf.b0c9f6","type":"mqtt in","z":"eff5d6e6.236338","name":"","topic":"alarm_clock/received","qos":"2","datatype":"auto","broker":"9e83409.d55cfc","nl":false,"rap":false,"x":2200,"y":1520,"wires":[["dd14cb9.4e59838"]]},{"id":"9e83409.d55cfc","type":"mqtt-broker","name":"Local Host","broker":"127.0.0.1","port":"1883","clientid":"","usetls":false,"protocolVersion":"4","keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","birthMsg":{},"closeTopic":"","closeQos":"0","closePayload":"","closeMsg":{},"willTopic":"","willQos":"0","willPayload":"","willMsg":{},"sessionExpiry":""}]

I see the messages clearly in a debug node (eg):

13:20:14@6,1

So in that spirit I add another line:

client.publish("alarm_clock/next","OK")

I then create another MQTT IN node and set it as so:

[{"id":"7af3c479.02f0ac","type":"mqtt in","z":"eff5d6e6.236338","d":true,"name":"","topic":"alarm_clock/next","qos":"2","datatype":"utf8","broker":"9e83409.d55cfc","nl":false,"rap":false,"x":960,"y":1310,"wires":[["931ebc46.313478","6e6d67af.fec578"]]},{"id":"9e83409.d55cfc","type":"mqtt-broker","name":"Local Host","broker":"127.0.0.1","port":"1883","clientid":"","usetls":false,"protocolVersion":"4","keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","birthMsg":{},"closeTopic":"","closeQos":"0","closePayload":"","closeMsg":{},"willTopic":"","willQos":"0","willPayload":"","willMsg":{},"sessionExpiry":""}]

Excuse the fact it is disabled

I stick a debug node onto it and wait.

{"topic":"ERROR_REPORT/Alarm_Clock/LCD message handling flow/alarm_clock/next","payload":"OK","qos":0,"retain":false,"_topic":"alarm_clock/next","_msgid":"b190ae41.af86f","error":{"message":"Unexpected token O in JSON at position 0","source":{"id":"6e6d67af.fec578","type":"json","count":1}}}

Where's the elephant?

I can't understand what is wrong with this.

It happily accepts the stuff I am sending back with text - which isn't a JSON structure as far as I know.

Yet, when I want to send back a simple OK.... It spits the dummy.

2

After my normal Bashing head against wall it has started to behave itself.

Partly because I removed the JSON node. But I didn't put one there originally as the one which works doesn't have one.

I put one there in an attempt to obey the rules of MQTT.

3

What rule of MQTT were you trying to obey?

4

So rather than having to put everything into the payload part of the message.

At the sending end, it gets the entire msg structure and puts it into a new msg.payload structure.

I'm still not sure it does work.

5

I still don't understand what rule of MQTT you were trying to obey.

6

@Colin Andrew is refering to the fact the MQTT nodes only publish msg.payload and not the full msg object.

7

Ah, some strange new use of the word 'rule' with which I am unfamiliar.

Thanks.

8

It is my failure to understand English vocabulary.

I called it a 'rule' as it has to be obeyed if you want to send complicated (not the right word maybe) messages.

9

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