basically tech

32 How Skype gets round firewalls

Friday 15th December, 2006

Have you ever wondered how two Skype (and other P2P) clients exchange data, despite the fact that both machines are each sitting behind a firewall that only permits outgoing traffic? Read this article from Heise Security.

Peer-to-peer software applications are a network administrator's nightmare. In order to be able to exchange packets with their counterpart as directly as possible they use subtle tricks to punch holes in firewalls, which shouldn't actually be letting in packets from the outside world.