I'm writing a simple Python client using Paho MQTT to communicate with mosquitto. I'm running into some issues with client.disconnect() and more specifically client.loop_stop().

According to the Paho docs, loop_start() is used to start up a threaded network loop. I've found that the most reliable way to call this is immediately after calling client.connect(). Apparently calling it just prior can have some unexpected effects. Anyway, for me this works fine.

The issue is around when I call client.loop_stop() around the time I wish to disconnect. Some online tutorials show that the best place to call this is in the on_disconnect handler, to be sure that the disconnection has fully completed, and so that any pending subscription or unsubscription attempts have been fully handled by the broker. This appears to work, but if I then attempt to reconnect (by a call to client.connect()) then the connection attempt does not work correctly - the client state gets stuck midway through, and the mosquitto broker only reports the following:

1642374165: New connection from 127.0.0.1:39719 on port 1883.

And nothing else. The connection has not worked. I'm not sure if the Broker is waiting for something from the Client (most likely?), or the Client has sent bad data to the Broker and triggered some kind of issue, but whatever the case, the connection is not valid.

If I move the loop_stop() call to just prior to the call to client.disconnect(), I get much more reliable behaviour, and the broker shows a proper subsequent connection attempt:

1642375893: New connection from 127.0.0.1:38735 on port 1883.
1642375893: New client connected from 127.0.0.1:38735 as client0 (p2, c0, k60).
1642375893: No will message specified.
1642375893: Sending CONNACK to client0 (1, 0)

However I understand that this may cause other issues - in particular, the disconnection may occur before any pending subscription or unsubscription requests have been fully processed, since the network loop is terminated before the disconnection is performed.

What I'd like to know is what's the official word on how to do a clean disconnection and terminate the network loop thread properly, without resorting to arbitrary time.sleep() delays to give things enough time to work themselves out.