phieber

Does it also hang if you restart the broker only?

Hi Franck, to be quite honest, I have no idea what was the issue anymore. However, I hope that someone else will benefit from your answer. Thanks take care Patrick...

Have you tried to connect from the very same subnet to the broker, using another client like an Android App? Are you using the ESP-01 with 8Mb flash?

I can also confirm that it works with Mosquitto (>=1MB ESP8266 Flash). Reliably over serveral days is a different story though ;) But that's where umqtt.robust comes into play