Getting the program name that is listening on a specified port

Sometimes we need to find out which program is listening on a specified port.

In Linux, we can use:
netstat -natlp

-n, --numeric don't resolve names
-a, --all, --listening display all sockets (default: connected)
< Socket >={-t|--tcp} {-u|--udp} {-w|--raw} {-x|--unix} --ax25 --ipx --netrom
-l, --listening display listening server sockets
-p, --programs display PID/Program name for sockets

In windows, we can use fport which can be downloaded in the internet.

Its official website: http://www.foundstone.com/us/resources-free-tools.asp