Amazingly back about 1997, it was still possible to have PCs connected to the Internet without firewalls or proxy servers. However the bad guys soon got active and a year or two later it was becoming much too dangerous to connect without some form of protection. This had the side effect that writing software to connect to other computers on the Internet became a bit messier. NAT (Network Address Translation) is common and present problems of it's own,
Developing P2P applications to work with firewalls, NAT and proxies is somewhat challenging. Google think so too and that is why they've produced LibJingle which is open-source C++ code with sample applications for building a peer-to-peer applications. It handles creating network connections (through NAT and firewall devices, relay servers, and proxies), negotiating session details (codecs, formats, etc.), and exchanging data. Plus additional tasks such as parsing XML, and handling network proxies. It's licensed under a BSD type license so free for commercial or non-commercial and uses the Jabber (i.e XMPP protocol) for exchanging data.
- Link to C++ Code Library
hey david I just want to thank you for your post Ive been intrested in peer to peer communications lately and this has come to be of much use.