Which process is listening on a given port on OSX?

You want to find out which process is listening on a port in OSX.

Just open a Terminal and write:

lsof -i :80

to find which process is using port 80

More Info

lsof comes from list open files

-i selects the listing of files any of whose Internet address matches the address after it

:80 part of the address that we're interested in - the port number