“Anatomy: A Look Inside Network Address Translators” by Geoff Huston: www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_7-3/anatomy.html

UDP hole punching www.brynosaurus.com/pub/net/p2pnat

Kqueue: people.freebsd.org/~jlemon/papers/kqueue.pdf

libevent: www.monkey.org/~provos/libevent

libjingle: code.google.com/apis/talk/about.html

Skype: www.skype.com

NATcheck: midcom-p2p.sourceforge.net (My code is derived partly from this)