Hi all, if you’ve just upgraded mosquitto server on some flavour of linux and wondered why all your mosquitto subscribers and publishers on your network have just started failing, you may have fallen foul of this:

the new mosquitto 2.0 requires a ‘listener’ be configured to the ports required, or else it will only listen to the localhost:1883.

So if all your clients start failing after, edit the configuation and add the following line to the top:

“listener 1883”

See the post here for more information: https://mosquitto.org/documentation/migrating-to-2-0/