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    Online multiplayer turn-based game with UDP

    RickyngkRickyngk Member
    edited March 2013 in General questions
    Hi,

    I'd like to make a Online multiplayer turn-based game (such as play chess). I decide to use UDP.

    For client discovery, I use UDP punch hole technique http://www.brynosaurus.com/pub/net/p2pnat/

    For turn-based controlling, I use the following mechanism:
    + Suppose that a host place two roles: host and client too
    + Client works in 3 state: LOCK (not in turn), INPUT (in turn), and SYNC (submit data to server), with two important properties: seq (sequence index), and turnIndex (turn index of each client)
    + Server send update data to clients frequently. Data include two important properties: seq (sequence index) and turnIndex (notice which client is in turn)


    Client state diagram: https://sites.google.com/site/sbskit/papers/online-multiplayer-turn-based-game-with-udp/client_state.png?attredirects=0

    Host flow:
    seqNo = 0
userInTurn = 0
while (true)
    if receive_submit() then
        seqNo = seqNo  + 1
        userInTurn = get_next_turn()
    end
    update_game_logic()
    deliver_to_all_clients(seqNo, userInTurn, gamedata)
end
    Client flow:
    seqNo = -1
function On_Receive_Data_Update(ServerSeqNo, currentTurnIndex, gamedata)
    if ServerSeqNo >= seqNo then -- valid seq
        if ServerSeqNo > seqNo -- change state
            if state is LOCK then
                if currentTurnIndex == turnIndex then
                    switch_to_state(INPUT)
                end
            elseif state is INPUT then
                if currentTurnIndex != turnIndex then
                    switch_to_state(LOCK)
                end
           else
                if currentTurnIndex == turnIndex then
                    switch_to_state(INPUT)
                else
                    switch_to_state(LOCK)
                end
           end
        end
 
        update_game_with_data(gamedata)
    end
end
 
function update_client_control()
    if state is INPUT then
       update_game_input()
       if hasEndTurn() then submit() end
    end
end
    See diagram in attachment

    Would you please give me your idea about my work. Any mistakes, problems, and your suggestion.

    Thank you in advance!

    Likes: TheOddLinguist

    http://www.guava7.com/
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    Comments

    • atilimatilim Maintainer
      edited March 2013
      @Rickyngk I have little information about this issue. But afaik, UDP hole punching is really hard to implement. And your clients needs a common server to pass through NAT and hole punch between them. Isn't it easier and more stable to use a server to orchestrate all network communication instead of hole punching?

      I think hole punching is (only) useful when you need to send large amount of data (such as file transfer or audio/video communication) between clients. Otherwise, communication through a server is preferable.
      http://en.wikipedia.org/wiki/Cytorus
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    • gorkemgorkem Maintainer
      @Rickyngk how frequent are you sending data? can push notifications be an option?
      +1 -1Share on Facebook
    • RickyngkRickyngk Member
      edited March 2013
      @atilim: I don't use server as a centralize system, and give host-role for client because of some reasons:
      + I wanna keep server in low CPU (discovery & forward only) so could increase CCU
      + If one server is not enough, I can use another one easily (they take role as client discovery and message forwarder at not, not game logic)
      + developer can develop game in client, no need server code (for simple game)
      + udp (or tcp) punch keeps traffic transfer thought server down

      Is it weird ? :D

      @gorkem: I send one data package per second.
      About push notification, you means local or remote notification? I don't know how does it work in this case :D
      http://www.guava7.com/
      +1 -1Share on Facebook
    • atilimatilim Maintainer
      edited March 2013
      @Rickyngk I think the main problem is that UDP hole punching is extremely hard to implement correctly. Therefore even for realtime MMO games, it's not used (or I haven't seen a real world example).

      not weird but insane :)

      Centralized systems also have some advantages like:
      - it's easy to modify game logic
      - it's hard to cheat
      http://en.wikipedia.org/wiki/Cytorus
      +1 -1Share on Facebook
    • gorkemgorkem Maintainer
      @Rickyngk I meant (remote) push notifications. Yours can be a good example to benefit from push.
      +1 -1Share on Facebook
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