Socket IO Server to Server

I realize this is an old post, but I was working on something similar and decided to come back and contribute something as it got me thinking.

Here's a basic Client -> Server 1 -> Server 2 setup

Server #1

// Server 1
var io = require("socket.io").listen(8099); // This is the Server for SERVER 1
var other_server = require("socket.io-client")('http://example.com:8100'); // This is a client connecting to the SERVER 2

other_server.on("connect",function(){
    other_server.on('message',function(data){
        // We received a message from Server 2
        // We are going to forward/broadcast that message to the "Lobby" room
        io.to('lobby').emit('message',data);
    });
});

io.sockets.on("connection",function(socket){
    // Display a connected message
    console.log("User-Client Connected!");

    // Lets force this connection into the lobby room.
    socket.join('lobby');

    // Some roster/user management logic to track them
    // This would be upto you to add :)
    
    // When we receive a message...
    socket.on("message",function(data){
        // We need to just forward this message to our other guy
        // We are literally just forwarding the whole data packet
        other_server.emit("message",data);
    });
    
    socket.on("disconnect",function(data){
        // We need to notify Server 2 that the client has disconnected
        other_server.emit("message","UD,"+socket.id);
        
        // Other logic you may or may not want
        // Your other disconnect code here
    });
});

And here's Server #2

// Server 2
var io = require("socket.io").listen(8100);
io.sockets.on("connection",function(socket){
    // Display a connected message
    console.log("Server-Client Connected!");
    
    // When we receive a message...
    socket.on("message",function(data){
        // We got a message. I don't know, what we should do with this
    });
});

This is our Client, who sends the original message.

// Client
var socket = io('http://localhost');
socket.on('connect', function(){
    socket.emit("message","This is my message");
    
    socket.on('message',function(data){
        console.log("We got a message: ",data);
    });
});

I am making this post a Community Wiki so that someone can improve this if they feel like it.

The code has not been tested, use at your own risk.

I had the same problem, but instead to use socket.io-client I decided to use a more simple approach (at least for me) using redis pub/sub, the result is pretty simple.

You can take a look at my solution here: https://github.com/alissonperez/scalable-socket-io-server

With this solution you can have how much process/servers you want (using auto-scaling solution), you just use redis as a way to forward your messages between your servers.

Yes, absolutely. Just use the Socket.IO client in your server application directly.

https://github.com/LearnBoost/socket.io-client

You can install it with npm install socket.io-client. Then to use:

var socket = io.connect('http://example.com');
socket.on('connect', function () {
  // socket connected
  socket.emit('server custom event', { my: 'data' });
});