I was wondering how the Half-Life 2 multiplayer protocol works in mods like Counter-Strike: Source or Day Of Defeat: Source. I believe that they use some kind of obfuscation and proprietary compression algorithm. I would like to know how different kinds of messages are encoded in a packet.
Half-Life 2, Counter-Strike:Source etc all use Valves Source engine. Valve has a developer wiki which covers a lot of stuff (its pretty cool check it out!)...
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Latency Compensating Methods in Client/Server In-game Protocol, Design and Optimization