Nothing is listening on that port.

Connection refused

The connection was answered, negatively

Nothing is bound to that port. The host is up, otherwise the attempt would time out.

Is anything listening

Bound to the wrong interface

A service on 127.0.0.1 refuses external connections even though local ones work. That is the usual shape of this error in containers.

Listening but not on that port

Scope: failure mode: Nothing is listening on that port.