Jim Plush has posted part one of a series of tutorials covering the use of sockets in PHP:

Anyway, here is a link to Part I on my socket programming tutorial. This page is really aimed at getting you up to speed on what socket programming is all about and what all the commands refer to and what the parameters they take are geared to do. I'm planning on adding a section a week so we'll see how that goes.

In this first part he looks at:

• the basic socket functions
• TCP and UDP protocols
• the creation of a socket server in PHP

In the end, there's a code listing of a very simple socket server, one he illustrates the use of through a simple telnet to the localhost.