This applies to all servers:
Bind a different port for incoming requests.
If the Server requires a Database connection, all you have to do is create a secondary Database for the new server, no need to switch from port 3306 on any of the servers.
Yes it can be Any port -- Above 4000. Preferably in the 20000-22000.
I usually use 4444, 4460, 4455 for ASP.NET so try those first.