I always am needing to know which ports are being used by my computers. Whether it is for security reasons or for debugging port accessing programs, Advanced Port Scanner is a small, quick, easy-to-use and robust port scanner for Windows.

It is multithreaded, so on relatively new machines you can scan ports in just a few seconds. You can download the latest version here: http://www.radmin.com/products/utilities/portscanner.php.

By default it shows a range of IP addresses from 192.168.1.1 to 192.168.1.255, so you can scan this range of 255 computers. You can set a limited range if you prefer to, but if you plan to use it in your home with only a few computers, leaving this range selected is ok since scanning is very quick.

Read more here http://technonigeria..com/2011/11/free-advance-port-scanning-tools.html

Good. Google country ip block. you will know more.