How in the Tech

Online Port Forward Checking with uTorrent

By Adam Myers ⋅ April 24, 2009 ⋅ Tags: Internet, Networking

Port forwarding isn’t something a typical Internet user needs to be concerned with, though the necessity is becoming more prevalent. Stepping back for a second, port forwarding came about due to the popularity of NAT routers in the home – simple network devices that allow multiple computers to share the same network connection. Because of NAT, or network address translation, all computers behind the router – like in your house – share the same public Internet address. The address assigned to each of your computers is only known by devices on your network, every other compute in the world talk directly to your NAT router. It is up to the router to redirect traffic as necessary. Without getting any further into the technical details, a port forward basically opens a port on your router and any request to that port gets redirected to a computer (and port) in your internal network.

Every day usage of the Internet rarely requires any port forward definitions. However, some situations do warrant a port forward to function correctly. The two most likely for a home user are XBox Live and Peer 2 Peer applications. Without a correctly configured port forward the performance of the application or device will be affected or worse, not work at all. As every home NAT router is configured differently – they all basically follow the same principle design; navigate to the routers web address and configure the options through a web interface.

The whole process isn’t nearly as difficult as it may sound but how do you know if you have the port forward defined correctly? For applications that either work or don’t, that’s a pretty easy thing to determine. But what about situations where performance is degraded by a misconfigured port forward? The popular torrent application, uTorrent, has a web service that can test your port forwarding configuration. While it may sound like this only works for torrenting, it actually works with anything as it is only testing that the provided port does respond correctly.

In your browser navigate to http://www.utorrent.com/testport.php?port=12345. The resulting page will inform you on whether port 12345 is open. You can then substitute your desired port for 12345.