Comment Re:GUI Code Only (Score 1) 175
Most SIP clients I've seen support STUN, which allows two NAT'd clients to talk to each other. The basic way that it works is for both clients to send a UDP packet to the STUN server. Their stateful NATs then set up a mapping from the public port to the private port. The server then forwards the address and port to each of the parties and then they can communicate with each other on that port. This needs a server set up on the public Internet, but so does Skype (so you can find the peer to peer network).
You just made fearlezz's point for him, I've highlighted the points where you did it. Yes, Skype needs servers, but the whole point is that Skype provides servers, some penniless foss project isn't going to provide servers which can cope with 18,989,413 clients at the same time (number plucked from Skype right now, the peak is probably higher).