Idea for online multiplayer turn-based game with UDP

Dear,

Online multiplayer turn-based game mentioned in this case is like chess, caro (gomoku), Othello online game. Each player makes a move in his turn, submit to host, and wait for other players turn.

Desired criteria:
+ Target: mobile
+ Simple, design for max 4 players per game
+ Keep server in low cost (CPU, bandwidth, transfer rate)
+ Available auto-reconnect if any

So I decide to use UDP. Server works like client discovery and message delivery at all. There’re two problems need to solve:
+ Package transmission mechanism: use UDP punch hole http://www.brynosaurus.com/pub/net/p2pnat/
+ Turn-based mechanism

For turn-based controlling, I have an idea as following:
+ Suppose that a host places two roles: host and client too
+ Client works in 3 states: 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)

Host work flow:

Code:

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 work flow:

Code:

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

Please see full post with figure at http://www.guava7.com/2013/online-multiplayer-turn-based-game-with-udp/

This is only a theoretically mechanism. Point me out if I make any mistake . Thank you in advance!

 

Apple API in this case is a good point, I'm learning to use it. But it's not cross-platform

 

Thank @Hercule, a lot of things to do with UDP, I'll take account, and do a testbed for some scenarios, maybe UDP for discovery & TCP for p2p connection in game
@TheBunny: thank for share, I' cloning https://github.com/lsalzman/enet , hope I could understand source code quickly