Sockets are used nearly everywhere, but are one of the most severely
misunderstood technologies around. This is a 10,000 foot overview of
sockets. It's not really a tutorial - you'll still have work to do in
getting things operational. It doesn't cover the fine points (and there
are a lot of them), but I hope it will give you enough background to
begin using them decently.
This document is available in several formats, including PostScript,
PDF, HTML and plain ASCII, from the Python HOWTO page at
http://www.python.org/doc/howto/.