MQTT subscribe Remaining Length encoding is incorrect
See this discussion for background, also MQTT spec V3.1.1 section 2.2.3.
This may be academic as its main impact is if the topic field is long. This is to record the existence of the issue.
The current encoding stores Remaining Length in a byte. It should be stored as a Variable Byte Integer as per .publish. This will cause a failure if Remaining Length is greater than 127, therefore imposing a limit on the length of the topic field.
I can submit a PR if the maintainers think this is worth fixing.
umqtt subscribe to topic with 23 bytes fails
Hi,
I can't subscribe to topic longer than 122 bytes. Publishing works fine!
I kindly ask you to verify and hopefully fix it
Thanks a lot
Danny
OK - working:
#122 bytes
mqtt.subscribe(b"/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/2")
but one more character:
#123 bytes
mqtt.subscribe(b"/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/234567890/23")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "test.py", line 169, in <module>
File "umqtt_simple.py", line 154, in subscribe
File "umqtt_simple.py", line 173, in wait_msg
OSError: -1
this might be related to #163 which also deals with 127 bytes
it might be related to https://github.com/micropython/micropython-lib/blob/f20d89c6aad9443a696561ca2a01f7ef0c8fb302/umqtt.simple/umqtt/simple.py#L148 as this is hitting the 128...
It looks like the subscribe method needs to handle variable length encoding of the payload size, in the same way that connect and publish do.
This appears ot have been fixed in the linked MRs/commits. Proposing to close this issue.
Looks like the author's PR was closed last year without merging, so I think this may still be an issue.
I had the same issue and @SpotlightKid fix worked for me. Sad that the PR is not merged