POP3 or other servers in php

I'm looking a POP3/IMAP server written in PHP. Or failing that, any socket-based sever would help me by being an example I could base my own on. I know there are a million functions, routines and classes for talking to POP3/IMAP servers. That is not what I need. I need an actual service (or example of one) in PHP, one that listens on a port and handles multiple incoming connections. What 'nixers would call a "daemon". I've done some RTFM and found quite a lot of interesting stuff in the manual and manual comments of the "Socket Functions" section. What I'm now seeking is real-world examples. Many thanks, Geoff.