A lot of people are using routers nowadays because most of us have more than one computers and sharing an Internet connection using router is better than using a switch with a computer acting as a server. When you have a router, it also pretty much acts like an outer layer of firewall because a hacker could only see the router and not directly to the computers in the network. That explains why a lot of trojan nowadays supports reverse connection to solve this problem. If you have a computer that connects directly to the Internet using an ADSL modem or switch, then there’s no need port forwarding.
In fact, there’s a lot of internet applications such as uTorrent, Limewire and etc that uses requires an open port to listen for incoming connections. If you’ve configured port forwarding for uTorrent, you’ll notice that the download is faster. Every software requires a unique open port that is not being used. Some software has fixed port number and some allows you to set a custom port number. Few days ago one of my friend called me to help him check on his CCTV because the person who sold him the CCTV system could not get the port forwarding working which means my friend could not access his CCTV from outside.
To some people, setting up port forwarding can be a daunting process. I’d say that some people find it tough because most the software itself is not capable of telling you if the port forwarding works or not. So you don’t know if it is a software, operating system or router problem which makes you checking every thing and eventually end up screwing it up even more.
Here is how to test if your port forwarding works or not. If you search in Google for “test open port” keyword, you’ll find a few sites which allows you to enter the port for testing. One of the example is CanYouSeeMe.org. It can only check for open ports on your computer. YouGetSignal is another web based open port tester which allows you to check on other people’s computer.
These web based port checkers works but in order for you to properly test if a port is open or closed, a program must be using the port on your system and accept incoming connections. Even if the port is not blocked by your router or firewall the test will still fail if nothing accepts the incoming connection attempt. Meaning that if you’ve opened a port 5000 for uTorrent but uTorrent is not running, the port testers will tell you that the port is closed and cannot be reached.
The best method to test for open port or if you’ve configured port forwarding correctly is to use Simple Port Tester. This program will open the port, listen for the connection and help ensure a proper and reliable test as to whether or not your port forwarding is working.
As you can see that Simple Port Tester is able to verify that the port 5938 is open. As for port 80 which says “Address in Use”, that’s because my router is using it. At the right pane, it does show that the port 80 is online and can be reached even though at the left pane shows Failed. Simple Port Tester is free and runs on Windows 2000, XP, 2003, Vista, 2008, Win 7. You can grab the portable version of Simple Port Tester if you’re a tech guy like me.