Question

I’m trying to make two clients (players) contact each other (exchanging for example strings) through socket.io. I have this code on the clients (gameId is defined back in the code):

var chat = io.connect('http://localhost/play');
chat.emit(gameId+"", {
    guess: "ciao"
});
chat.on(gameId+"", function (data) {
    alert(data.guess);
});

While on the server I have this (which is one of the first things I do, not in routing of course)

var messageExchange = io
    .of('/play')
    .on('connection', function (socket) {
        socket.emit('message', {
            test: 'mex'
        });
      });

Basically I create the channel, then when users connect they use the channel to exchange a message of the king “gameId” that only the both of them can read (using the on.(gameId+"" ... stuff.
My problem is that when players connect (first one, then the other), the first one that connected should alert the data received (because the second one that connected emitted a message). Does anyone of you know why this is not happening?

Thanks.

Answer 1

The socket.io server should act like a middle man. It can receive messages from clients and send messages to clients. It doesn’t act as a “channel” by default, unless you have the server relay messages from clients to other clients.

There’s a lot of good info on common uses on their website, http://socket.io and their repo, https://github.com/LearnBoost/socket.io

A simple example of a chat client could be something like this:

var chat = io.connect("/play");
var channel = "ciao";

// When we connect to the server, join channel "ciao"
chat.on("connect", function () {
    chat.emit("joinChannel", {
        channel: channel
    });
});

// When we receive a message from the server, alert it
// But only if they're in our channel
chat.on("message", function (data) {
    if (data.channel == channel) {
        alert(data.message);
    }
});

// Send a message!
chat.emit("message", { message: "hola" });

While the server could act like this:

var messageExchange = io
    .of('/play')
    .on('connection', function (socket) {
        // Set the initial channel for the socket
        // Just like you set the property of any
        // other object in javascript
        socket.channel = "";

        // When the client joins a channel, save it to the socket
        socket.on("joinChannel", function (data) {
            socket.channel = data.channel;
        });

        // When the client sends a message...
        socket.on("message", function (data) {
            // ...emit a "message" event to every other socket
            socket.broadcast.emit("message", {
                channel: socket.channel,
                message: data.message
            });
        });
     });