You might stumble across a bug using Firefox to connect to a Mosquitto MQTT service.
Symptoms experienced in the Firefox console:
AMQJS0007E Socket error:undefined
Firefox can’t establish a connection to the server at wss://localhost:9001/mqtt
This is likely due to an issue in protocol handling of HTTP2. Whilst Chromium does not attempt a HTTP2 connection in this case, Firefox tries it first and gets a reply from the server.
Workaround 1 (Firefox local):
Set `network.http.spdy.websockets` to `false` in Firefox `about:config`.
Workaround 2 (Server side):
Use a version of libwebsockets compiled without HTTP2 support.
Compile flag is `-DLWS_WITH_HTTP2=OFF` in cmake to build with http/2 support disabled.
You can find prebuild versions version in the