The default port that the Windows Remote Desktop Connection program listens on is 3389. However, you can change to any port you wish; maybe you find public networks block everything except port 80 and 433 (in which you could set it to 433) or you feel changing to a non-default port is better security wise. Whatever your case, you must edit the Windows Registry:

Hive: HKEY_LOCAL_MACHINE
Key: \System\CurrentControlSet\Control\TerminalServer\WinStations\RDP-Tcp\
Name: PortNumber
Type: REG_DWORD
Value: desired port number in Decimal format

Then if you use the Windows Remote Desktop Connection program to connect to the computer, follow the address you want to connect to with a colon and the port number that you changed to; for example 255.255.255.255:433.