Get process that bind a port

["Reuben D. Budiardja" <techlist pathfinder phys utk edu>]

Hello,
I am playing around with writing a program to bind to socket / port in my 
machine. Often time, I got the message:
bind(): Address already in use

So my question is, how do I find out which process bind to a certain port 
number ? For example, how do I find out what process use port 2345? Sometimes 
'ps ax' does not really show the process that I though bind that port number, 
although bind() gave the error message. Plus 'ps ax' does not really help 
unless you know the process name anyway.

Thanks for any help.
RDB