POA Proxy access and redirection

I know this is not the recommended solution for connecting with a GW client directly from outside but in this case it is a valid solution as the server is protected.
Following the setup in connection magazine:
Connection Magazine May | June 2004: Teacher's Pet

It is clearly stated that there is a one to one relationship and I have no problems to run several POAs on this DMZ server.
"All" I would like to know if there is a possibility to let users connect with their GW-Client without any port specification, incorrect port specification or default port 1677, and they are redirected correctly to their specific POA with the correct address so that a connection can be established.

Thanks for your help,