client notifications (Question ) about async-mqtt5 HOT 1 OPEN

The key feature of our library is the auto-reconnect and retry mechanism, which means that the Client will repeatedly try to establish a connection to the Broker regardless of the reason why the connection failed (temporarily unavailable Broker, loss of connection, wrong credentials,...).

As you have correctly observed, this means that if you provide the wrong credentials, the operation will keep trying to connect to the Broker without feedback. We covered this topic in our documentation in which we describe our auto-reconnect and retry mechanism and limitations that come with this design choice.

Currently, we do not have a logging mechanism that would notify you of such events. This is partly because we want easily customisable logging that provides zero overhead for users who do not need logging.

However, you can still inject your own logging lines into the code.
Specifically, in connect_op.hpp, I recommend logging in line 332, print the reason code (from the CONNACK packet) using rc.message() to inform you if you are using wrong MQTT configuration (credentials and connect properties).

from async-mqtt5.