Linux Network Management with "netstat"
The netstat (short for network statistics) command line tool helps in retrieving information such as network connections, network interfaces in use, routing tables, masquerade connections. It lists out all the TCP, UDP socket connections, and the UNIX socket connections. The common test case that almost everybody encounters to see whether a given background process says a web server running or not on the specified port. Apart from this kind of simple yet powerful test case, netstat is h