FreePortScanner is a free utility that allows you to know which ports on your computers are open and which are not, with a few simple clicks. With FreePortScanner you can scan all of your system's ports, as well as those that belong to another computer that's connected to your local network. To do this, all you need to do is input the correct IP address.
Furthermore, although FreePortScanner includes the TCP port ranges that it is analyzing, you can manually assign others too. The program has a simple interface that lists all the ports you have assigned to it, along with other data like the IP address, the port number, the name and a small description of it.