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I am thinking about creating a networking game.
The game should be a 2D platform shooter, created with Libgdx and Box2D.
For the networking I planed following structure:

  • Server and client are 2 programms
  • Server handles ALL the ingame logic
  • Client sends key/mouse inputs
  • Server reacts on those and updates the whole level
  • Server sends those updates (if possible 45 times per second so no client side interpolation needed)
  • Client gets updates and updates its local level/world by using the received updates
  • Client draws the things in its view frustum

First question: What do you think about this structure?
Next question: 45 times per second could be a lot of data upload from the serverside, if there are a few players which shoot a lot of bullets (player and bullet positions need to be send).
To limit the upload needed i thought about using view frustum culling and send only the data/updates the client will actually see.
Now i have seen the KryoNet method sendToAllTCP and wondered, if this method is somehow more efficient and could somehow upload the data only once, instead of once per client.
I am not that experienced with networking and i don't really think that it is possible to have 1 upload for more then one client. But to be sure i ask.
So is it more efficient to send every update of the level with sendToAllTCP or is it more efficient to send once for every client and then only things they can see?

Robert P
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1 Answers1

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KryoNet is open source, and you can see what it is doing here: https://github.com/EsotericSoftware/kryonet

The sendToAllTCP method is here: https://github.com/EsotericSoftware/kryonet/blob/master/src/com/esotericsoftware/kryonet/Server.java#L447

The sendToAllTCP method just loops over the TCP connections and sends the same data to each one. There is a comment in the source that they should only be serializing the data once, and send the serialized object multiple times, but its not doing that yet.

Generally, the ability to send data to multiple hosts on a single send is called "multicast". For lots of reasons it is not generally available and is only useful in highly specialized situations. See http://www.tcpipguide.com/free/t_IPMulticasting.htm

The performance problems you're going to run into are more likely around internet latency than on the server's raw ability to send packets. I wouldn't worry too much about optimizing TCP connection sends just yet.

P.T.
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  • Thanks for the informations. I thought that the question about having one upload for more then one client is a stupid question but it seems like this really exists^^ Its interesting to know. For the latency problem: I don't think that my game, if i am even able to make it, will run online. I am thinking more about Lan, where latency problems don't exist that much. Thanks a lot! – Robert P May 12 '14 at 06:01