As far as I can understand, the home work given is let people gets hands on activity with network programming. So might take a look at www.twistedmatrix.com, few example use case of twisted
Chat comet site using python and twisted,
http://lists.canonical.org/pipermail/kragen-hacks/2005-April/000409.html,
http://code.google.com/p/twisted-chat-example/.
This one uses plain socket programming http://code.activestate.com/recipes/531824-chat-server-client-using-selectselect/,
http://ankurs.com/2008/05/creating-a-simple-chat-application-with-python/.
This one is based on gevent.
For simple chat room emulation without use of socket programming, here is the example gummi.
A real life use case at sourceforge.
