Thank you Kevin; I have a copy of "Unix Network Programming" book by W. Richard Stevens, 1990 edition. I hope that's not too old to be useful. I have started to read it. But perhaps you can clarify one thing for me that might be the basis of my misunderstanding. Does the port number in the header end up as, or refer to, a specific physical location on my computer (memory) or is it just a label that tells my cpu which program to call in order to process the message? On Wed, 2005-07-27 at 11:37 -0400, Kevin Everets wrote: > I recommend that you read the "Unix Network Programming" and "TCP/IP > Illustrated" books by W. Richard Stevens (available from the Ottawa > Public Library... currently checked in, even). They should answer > your basic TCP/IP and networking questions... the other > misunderstandings can be dealt with using other texts or here (after > you've read the above). > > Kevin.