How to Find the Port Number of the Remote Host
Although the default port number for the Remote Desktop Connection software is 3389, that port can be changed editing a specific key in the Windows registry. If you want to figure out what port number a computer is using for incoming remote desktop connections, you need to log in to that computer locally, open the Registry Editor and look at the key that sets up that port for use in the computer.
Log in to the computer that hosts the remote connection.
Click "Start" and then type "regedit" into the search box on the Start menu.
Go to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" in the registry.
Note the value for the "PortNumber" registry key; this is the port of the remote host on the computer.