A useful utility for discovering which process is bound to a particular port is the tool 'lsof', available from ftp://vic.cc.purdue.edu/pub/tools/unix/lsof.
f can be used for many purposes (mostly to do with investigating open files and network sockets), see the man page for complete documentation; the following merely describes how to use it to determine the process running on a particular port:
lsof -i :[port-number]
Note that you will probably need to be root in order to get any output.
An example is given below:
localhost:~# lsof -i :80COMMAND PID USER FD TYPE DEVICE SIZE NODE NAMEzeus.web 23020 root 12u IPv4 1142747 TCP *:www (LISTEN)zeus.web 23025 root 14u IPv4 1142747 TCP *:www (LISTEN)
