QUERY · ISSUE

MQTT Disconnect socket write then close

openby AngeloFaticaopened 2023-08-16updated 2023-08-16

When there are network issues and I want to disconnect from mqtt client, the socket writes are blocking and cannot be changed (I havent been successful) so it will just hang on the self.sock.write(b"\xe0\0") line in the disconnect function of simple.py. Is this a necessary action, or can I not write that byte array and just close the socket so that I do not have to worry about hanging on the write indefinitely?

CANDIDATE · PULL REQUEST

umqtt.simple: add force_close parameter to disconnect() to ensure soc…

closedby jzafranopened 2017-12-30updated 2018-10-12

Add force_close argument to umqtt.simple.MQTTClient.disconnect() that, when set, ensures socket.close() is called even if there's an error while sending the disconnect message to the MQTT server.

The default behavior is the same as before - I'm tempted to change it; I believe it would be a better default, but I don't want to break any backward compatibility.

Assessment

S Sonnet · high

Both items target disconnect() in umqtt/simple.py and share the same concern: the socket not being reliably closed when network issues occur during disconnect. However, the PR's force_close parameter only ensures socket.close() is called when the write raises an exception (OSError). The issue's core problem is a blocking write that hangs indefinitely — the code never reaches socket.close() because the write never returns, not because it throws. force_close=True would not help in that scenario. The PR addresses a related but distinct failure mode (write error vs. write hang).

Suggested action

Reference PR #243 in issue #716 as partial context. The issue warrants a separate fix addressing non-blocking socket configuration or a socket timeout before the write in `disconnect()`. PR #243 is worth merging independently as it improves error resilience, but does not close issue #716.

MQTT Disconnect socket write then close

umqtt.simple: add force_close parameter to disconnect() to ensure soc…

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