The Windows Remote Desktop program (also known as RDP) uses port 3389 by default to communicate back and forth between computers that are connected together. In the event that you or the computer you are connecting to is behind a router, you will need to alter the settings of the router to forward port 3389 from the router to the computer you are attempting to connect to.
Find out the Computer's IP Address
To correctly forward port 3389, you'll need to know which computer you are forwarding the port to. This information is easy to find out, though. Simply go to the computer, click "Start," click "Run," type "CMD" and press the "Enter" key. Type "ipconfig /all" and then look for the IP address listed next to the "IP Address" label for your network connection. Write down this number, because you'll need it later.
Log Into Your Router
Home Internet routers have Web-accessible control panels you can log into by opening a Web browser and going to the IP address of the router. This IP address is usually 192.168.1.1, but it differs depending on the type of router you have. Check your router manual for information on exactly what this IP address is. You can also pull up a command prompt (click "Start," "Run," type "cmd" and then hit "Enter") and type "ipconfig /all" into the window. The "Default Gateway" IP address is the IP address of your router. Enter a username and password to log in to your router's control panel. This information differs from router to router, so reference your router's manual for this information.
Make Changes to your Router's Settings
Once you are inside your router's control panel, look for the "NAT," "Port Forwarding" or "Applications and Games" section and click on it. The name of this section differs from router to router, but once you are in the right section, you'll see a list of text entry boxes where you can enter in port numbers and IP addresses. Set the forwarding ports to be 3389 in all cases. Type in the IP address of the local computer as the one those ports should be forwarded to. Save the settings and restart the router (if necessary). Once this is all finished, you'll be able to connect to your local computer from the outside world using the Remote Desktop protocol.
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