Detect port number of SASL AUTH request?

Hi, this is partly Postfix related, but I want to know if there could be way to distinguish port of the SASL AUTH request to segregate user services.

Currently I use unix listener for dovecot sasl auth, but could change to inet_listener.

Only way I can think is to have different SASL AUTH services for each master.cf entry where its needed. But is it possible for Dovecot to have more than one SASL AUTH services with different configuration setup? It would be nicer if there was a way for Postfix to tell Dovecot about the port the client connected on.

Or maybe it can be done with a SASL realm? I'm not sure how? Any help please?