In Linux, How do you find find out what process is occupying what port ?

Looking simple command line solution to find out what ports are occupied by what process, in Linux or Unix in general.In Linux, How do you find find out what process is occupying what port ?
I have used lsof to do this. In my case it was on Solaris for determining a free port for Tuxedo app server.



The command I used shows what proc is using TCP port 45003, it as follows:



lsof -i TCP:45003



Hope that helps