net-mqtt v0.5.0.2 Release Notes
Release Date: 2019-09-15 // over 4 years ago-
With a few attempts to misuse the library, I found some places where error messages weren't useful enough. There were still two cases where failures turned into indefinite STM errors instead of more informative errors. 1) when the broker declined your connection and 2) when the broker refused your connection. These are errors at differnet layers, so were addressed differently, but should be informative in both cases now.
Unsubscribe was apparently broken in MQTT 5 as well. I'd never tried to use it, and just happened to notice it wasn't quite right.