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I have an working project where, with the MQTT-IN node, i subscribe to a local Mosquitto Broker. But when i want to change to MQTT Version 5 it doens't work. On every other Subscriber (mqttx) it was working after just changing the version in the options somewhere. But after changing it on the configuration-node it doesn't connect anymore. Do i have to change anything else to get it working or am I missing something?

Thanks!

Bottom line up front: The Paho MQTT client sucessfully connects to my Mosquitto broker, but immediately disconnects when I try to publish a message or when it receives a message from a topic it's subscribed to. I've tried changing Mosquitto's listening port and authentication settings, and using two different versions of Paho MQTT, and I still have the same problem.

Now let's get into detail.

Intro: I'm making a dashboard for some facial recognition devices that communicate through MQTT. I set up a Mosquitto broker and I've had no problems connecting to it and communicating with the devices using the Paho MQTT client for Python (I made a kind of server to sync the device's info to a database). Now I'm making the web interface, so I added a WebSockets listener to my mosquitto.conf and wrote a script using the Paho MQTT library for Javascript to connect to it, subscribe to topic sgdrf/out, send a simple JSON message to topic sgdrf/in to get the list of online devices, and process the response of the Python server once it arrives.

Problem and attempted solutions: I ran the Django server, loaded the web page and opened the JS console to find that the MQTT client successfully connected to the broker but immediately disconnected when it tried to publish the message to topic sgdrf/in. Here's each line of console output with their explanations:

1. The message produced by the onSuccess function, which indicates that the client successfully connected to the Mosquitto broker:

   Conexión exitosa al broker MQTT.

2. In the onConnected function, I added console.log(uri) to see the URI used by the client to connect to the broker. I got:

   ws://localhost:61613/

3. After printing uri to console, I made the client subscribe to sgdrf/out and then print 'subscribed' to console:

   subscribed

4. Then I call get_online_devices(mqtt_client), a function which creates a simple JSON string and publishes it to the topic sgdrf/in. But first, it prints the strign to the console so that I can check it (just in case):

   {"operator":"GetOnlineDevices","messageId":96792535859850080000,"info":{}}

5. Then, when the publish method is actually executed, is when I get this error (captured by the onConnectionLost function):

   Pérdida de conexión con el broker MQTT: AMQJS0005E Internal error. Error Message: message is not defined, Stack trace: No Error Stack Available (código: 5)

I checked the Mosquitto log file and it only says when a new client was connected and then when it was disconnected because of a socket error (each time for every page reload). Tail of /var/log/mosquitto/mosquitto.log: