General Peer-To-Peer architecture

In a perfect theoretical开发者_如何学C network, i'd be able to open connections from any peer to any peer. Life however works in a different way. If I'm to create a global peer to peer application, how do I get over this connectivity hurdle without investing in my own server farm.

My goal is to build an application where packets of xml can be sent between peers.

You need to learn about NAT traversal techniques. The simplest solution to implement is UDP traversal. You can also consider the JXTA/JXSE framework for a TURN-like NAT traversal implementation.

In all cases, you will need at least one server with a public IP address (but that's not a farm of course...)