sorry bugger writes "From the article: "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." More under http://www.heise-security.co.uk/articles/82481"
A method of solution is perfect if we can forsee from the start,
and even prove, that following that method we shall attain our aim.