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So I'm writing a fairly simple game with very low networking requirements, I'm using TCP.

I'm unsure where to start in even defining/implementing a protocol for the client and server to use. I've been looking around and I've seen a few examples, for instance Mojang's Minecraft which uses a table of 'commands' the client sends the server and the server sends the client, with numbers of arguments and such.

What's a good way to do this? I've heard complaints about Minecraft's protocol because if you overread by a byte you ruin the entire stream.

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  • What language? I'm assuming c/c++/objc but if you are using java or something else common game networking libraries like GNE aren't going to work for you. Commented Aug 30, 2011 at 19:10
  • I'm using Lua at the moment, I may later use C on the server if it becomes necessity for performance (which is unlikely). And I'd like to use TCP to simply learn how to do some simple networking. Commented Aug 30, 2011 at 19:11
  • Why exactly was this edited to tag Lua? It's a language independent question... Commented Aug 30, 2011 at 19:34
  • @Mathew: I tagged it as Lua because per your comment above; you are trying to do this in Lua. If you feel that the tag doesn't belong; than remove it. Commented Aug 30, 2011 at 19:37
  • @Matthew, I think the language is relevant, otherwise something like Reflection could work quite well (only supported in Java and C# as far as I know) Commented Aug 30, 2011 at 19:49

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Game networking is a broad question, depending on what type of problem you are solving. TCP (may) not even be the correct choice for you.

For example - games that send movement of characters is typically done with UDP. The reason being that character movement isn't critical to the operation of the game, so some data loss of movement is "acceptable". That may be why sometimes your character "jumps" - some UDP packets were lost, or severely out-of-order.

UDP is argued as the preferred protocol for networked games. So before you even get started, carefully consider whether you are even picking the correct protocol.

Overall, I consider Glenn Fiedler's series on developing a networked game a fantastic read. I'd start here. He covers all of the basics of using UDP for gaming.

If you want to use TCP simply just to get a handle on TCP - then Minecraft is a reasonable example. A known list of commands that can be sent back and forth is a simple way to start. However, as you stated, is prone to some problems. This is more aligned with using the wrong protocol than how it was developed.

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Google "game networking library" and you'll get a bunch of results. GNE would be a good one to look at.

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In that case, just learn sockets.h inside and out. Pass UDP between game clients. It's pretty easy stuff once you dig into a bit.
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I guess it depends on what your game is, what it mechanics are, what information is necessary. In any case I think this stack exchange https://gamedev.stackexchange.com/ is more suited to answer your question.

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Gamedev.net's networking forum has a great FAQ covering these sorts of questions and many others, however, to make this more than a 'go-there-look-at-that' answer, I'll suggest some small improvements you can make. When using tcp, delivery is guarenteed, but this has a speed cost, which is fine if your not making a fps, but it means you need to get more from the data you do send, a great way to do this is via deltas/differentials, that is, sending only the change in state, not the entire game state, you can also validate your incoming packets for corrupt/anomalys data over and about tcp checks by predicting possibilities are allow, and with the same prediction, you can cut out even more data etc. But as others have said, this is a broad question, and not suited to getting truely helpful answers

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As you're coding in lua, the only library anyone uses is luasocket (though ZMQ is gaining ground).

You're really going to have several protocols going: TCP for data that must be received (eg, server commands such as changemap or you_got_kicked, conversations and such; then use UDP for non-compulsory data, or data that quickly expires (eg, character positions).

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