You may find yourself wanting to use Remote Desktop (RDP) with a different port from the default 3389.

The senario I had was two users wanting to connect to their office based computers.  I needed to redirect port 3389 to one computer and another port (3390) to the other computer.  I have taken some of the information from Microsoft Knowledgebase Articles 306759 and 304304.

Firewall Port Redirection:

When you are connecting to a remote computer, you must ensure that if you have a firewall you redirect the chosen ports to the computers in question.  In this senario the only firewall is on the broadband router.  I'll give you an overview here, because each broadband router is slightly different in how you set these settings:

The router will probably be running a DHCP Server which automatically assigns an ip address to your computer.  You will need to setup the computers with static ip address to make sure that the ip address never changes.

Router:
IP Address = 192.168.0.1
Subnet Mask = 255.255.255.0

Computer1:
IP Address = 192.168.0.2
Subnet Mask = 255.255.255.0
Gateway = 192.168.0.1

Computer2:
IP Address = 192.168.0.3
Subnet Mask = 255.255.255.0
Gateway = 192.168.0.1

Computer1 will listen on the default port 3389. Computer2 will be configured to listen for RDP connections on port 3390.

Login to your router and locate the firewall.  It may already have a pre-defined port for Remote Desktop (RDP) which will be port 3389, if not create a custom rule as with port 3390.  Where the rule asks for a destination type in the computer you want the port to be forwarded to.

In the above example:
PORT 3389 -> 192.168.0.2
PORT 3390 -> 192.168.0.3

Now you need to configure Computer2 to listen on port 3390, see next step:

Changing the port on the RDP Server Computer (Computer you want to connect to):

Warning The Remote Assistance feature in Microsoft Windows XP may not work correctly if you change the listening port.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
307711  (http://support.microsoft.com/kb/307711/ ) Remote Assistance invitation file does not contain correct port number
To change the port that Remote Desktop listens on, follow these steps.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs.

• Start Registry Editor: START -> Run -> Type in REGEDIT -> Click on OK.
• Locate and then click the following registry subkey:
  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TerminalServer\WinStations\RDP-Tcp\PortNumber
• On the Edit menu, click Modify, and then click Decimal.
• Type the new port number (3390), and then click OK.
• Quit Registry Editor.

Note When you try to connect to this computer by using the Remote Desktop connection, you must type the new port.

Changing the port on the RDP ClientComputer (Computer you want to connect to the Remote Computer from):

To change the port number that the Remote Desktop client connects to, follow these steps:

Click Start, click All Programs, point to Accessories, point to Communications, and then click Remote Desktop Connection.
In the Computer box, type the computer name or the IP address of the computer that you want to connect to, followed by a colon (:) and the port number that you want to use.

For example, to connect to port 3390 on a computer that is named "MyXPPro," type the following information:
MyXPPro:3390
Click Connect.

To connect to port 3391 on a computer with IP address 10.10.10.1, type the following information:
10.10.10.1:3391
Click Connect.