Node.JS in Action, example 3.11

nodejs-in-action-3_11

var events = require('events');
var net = require('net');


var channel = new events.EventEmitter();
channel.clients = {};
channel.subscriptions = {};

//Add a listener for the join event that stores a user’s client object, 
//allowing the application to send data back to the user.

channel.on('join', function(id, client) {
    this.clients[id] = client;
    this.subscriptions[id] = function(senderId, message) {
        //ignore data if it’s been directly broadcast by the user.
        if (id != senderId) {
            this.clients[id].write(message);
        }
    }
    //Add a listener, specific to the current user, for the broadcast event.
    this.on('broadcast', this.subscriptions[id]);
});

var server = net.createServer(function(client) {
    var id = client.remoteAddress + ':' + client.remotePort;
    client.on('connect', function() {
       //Emit a join event when a user connects to the server, specifying the user ID and client object.
        channel.emit('join', id, client);
    });
    client.on('data', function(data) {
        data = data.toString();
        
        //Emit a channel broadcast event, specifying the user ID and message, when any user sends data.
        channel.emit('broadcast', id, data);
    });
});
server.listen(8888);