Remote Desktop is a multi-channel protocol that allows a user to
remote access or connect to a computer which has enabled Remote Desktop
server from another remote computer, through Local Area Network (LAN),
Wide Area Network (WAN) or Internet by using Remote Desktop Connection
client program. Microsoft Remote Desktop Protocol (RDP) server
application can be found pre-installed on Windows Server 2003, Microsoft
Windows XP Professional, Microsoft Windows XP Media Center Edition
(MCE), Microsoft Windows XP Tablet PC 2005 Edition, Windows Vista
Ultimate, and Windows Vista Business Edition. By default, Remote Desktop
is using port 3389 TCP (UDP to stream audio redirection) as the
listening port for any incoming Remote Desktop connections.
Although Remote Desktop server is using the default listening port of
3389 TCP and UDP, it’s possible to modify or change the listening port
of Remote Desktop to another port. It’s especially useful when the
remote computer is behind firewall which doesn’t allow incoming and
outgoing connections other than standard ports (Windows Firewall in
Windows XP Service Pack 2 (SP2) will automatically configure and open
required ports when user enable Remote Desktop to allow Remote Desktop
connections to the computer, if Don’t Allow Exceptions is not selected,
else user will need to manually open the Remote Desktop port in Internet
Connection Firewall on Windows XP SP 1 or earlier), or users unable to
configure the port forwarding for Remote Desktop if they’re behind
firewall or router’s NAT.
How to Change the Listening Port for Remote Desktop
Microsoft has a Knowledge Base article KB306759 that details how to modify and change the Remote Desktop listening port by changing registry value.
HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Control\TerminalServer\WinStations\RDP-Tcp\
If you don’t want to mess or modify in the Windows registry yourself, IntelliAdmin has a small free utility tool Remote Desktop Port Change (RDPRemotePortChange.exe) that allows users to change the Remote Desktop listening port on local computer or on remote computer across the LAN.
To change listening port for Remote Desktop for local PC (the computer that you’re using now), simply select Local System, or select Remote Computer for other computer and key in the desired computer name or IP plus authentication user name and password to change the listening port. Configure the required settings i.e. the new port number for Remote Desktop, and whether to reboot the PC after the change, and simply press Submit.
Note that Remote Assistance feature in Microsoft Windows XP may not work correctly if the the listening port of Remote Desktop has been changed. Beside, when want to connect or remote control this particular computer with non standard listing port by using the Remote Desktop connection from remote computer, the port number must be specifed together with computer host name or IP address ( ie hostname:3389) to connect to that specific port.