Making server logic independent of client interaction

Question

I'm trying to make a realtime multiplayer web-game in node.js with express framework and socket.io library. But I can't seem to make my server-side logic independent of client interactions. I want client to interact only when I (server side logic) want but I can't seem to be able to do that. For example:

I want 2 users to start playing a game. I have to first initialize the game, like set up environment, variables and stuff.. all in a separate, call it: The Game Logic. Only then can I "allow" the clients to interact.

But how am I supposed to carry on with my Game logic when my socket.on event is "calling the shots"? With socket.io you have to define triggers like

io.sockets.on('connection', function(socket) { socket.on('event', function(data) { //supposed this is fired when client hits an "interact with X" button }); }

All my logic seem to be dependent on these triggers. I only wanted client to be able to fire that event when I want (after I've set up the game env etc), but defining it like so, separated from my game logic, it creates problems like how am I supposed to transfer the execution control from socket into my game logic? And even if I managed to, there's that whole client "calling the shots" problem. I then have no control when client could want to interact.

Any advice what should I do?

The logic needs to run in a separate thread that handles client requests. Put client requests from your socket.on method into a message queue and your server chooses when to process the message(s). You'll probably need to keep that client socket open to have the server send a response at its time of choosing. The reason for that is that some networks will block connections initiated from the outside unless those connections are opened by the network admin. So, you probably won't see this on your LAN, but if you move to a WAN that's when your design may need a rewrite without considering this. — Dunk
– Dunk, Commented Apr 21, 2014 at 15:46

Emw · Accepted Answer · 2014-06-20 00:04:40Z

Your game object would typically be a separate prototype function (class). It might look like this:

Game = function() { var sockets = []; var pendingEvents = []; var interval = 500; // Process every 0.5s var init = function() { // Do game initialization stuff here // Start the game timer setInterval(function() { gameLoop(); }); }; // Do the actual game loop gameLoop = function() { // Do some work // Handle user events, starting with the oldest var message = pendingEvents.shift(); while ( null != message ) { handleMessage(message.socket, message.data); var message = pendingEvents.shift(); } // Do other stuff }; // Process a player's message event handleMessage = function(socket, data) { }; addSocket = function(socket) { sockets.push(socket); }; queueEvent = function(event) { pendingEvents.queue(event); }; return { queueEvent: queueEvent, addSocket: addSocket }; }

This game class gives you a skeleton that holds all the connected sockets (loop through to send a message to everyone) and does some game logic every 500ms. During the game loop it looks in the message queue for player events it needs to handle.

Now going back to your original socket code, you can inject player events into the game like this:

// This happens anywhere var gameInstance = new Game(); // Now watch for sockets io.sockets.on('connection', function(socket) { // Add the socket to the game gameInstance.addSocket(socket); socket.on('event', function(data) { // Push the client event to the game, game will handle it on its own terms gameInstance.queueEvent({ socket: socket, data: data }); }); }

Community · Accepted Answer · 2017-05-23 12:40:20Z

You need to make the client available for receiving a call.

You either "push" sample/source or setup a "client-server" sample/source

Another option would be to have the client call to the server at a scheduled time (like every 15 min) and if there is something you want to "say/do" it happens then.

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