i’ve been meaning to update the previous chat tutorial to include multiple rooms, here it is.

what i failed to cover in the previous example was how to send messages/broadcast information with socket.io. the following examples assume you define the module:

var io = require('socket.io').listen(app);
io.sockets.on('connection', function (socket) { .... });

from the server, emit to the client’s socket only, using the socket callback:

socket.emit('function', 'data1', 'data2');

from the server, emit to everyone but the client’s socket (to broadcast a message):

socket.broadcast.emit('function', 'data1', 'data2');

from the server, emit globally:

io.sockets.emit('function', 'data1', 'data2');

you see that io was initially defined as the socket.io module, so we emit to all its sockets.

one of the latest updates to socket.io now allows rooms/groups. for a client to join and leave a room:

socket.join('room1');
socket.leave('room1');

to broadcast information to a certain room (excluding the client):

socket.broadcast.to('room1').emit('function', 'data1', 'data2');

to broadcast information globally:

io.sockets.in('room1').emit('function', 'data1', 'data2');

on with the tutorial, in the new app.js, when a user connects and enters their username, he joins room1 by default and broadcasts (only to room1) that they’ve joined. i’ve also added a list of available rooms (room1, room2, room3) and a function that updates that list to reflect the user’s current room.

if the user decides to switch rooms, a client-side function switchRoom is called. the server listens for this call and tells the user’s socket to leave the current room and join the new room, broadcasts locations and updates the room list.

here is the updated app.js:

var app = require('express').createServer()
var io = require('socket.io').listen(app);

app.listen(8080);

// routing
app.get('/', function (req, res) {
  res.sendfile(__dirname + '/index.html');
});

// usernames which are currently connected to the chat
var usernames = {};

// rooms which are currently available in chat
var rooms = ['room1','room2','room3'];

io.sockets.on('connection', function (socket) {

	// when the client emits 'adduser', this listens and executes
	socket.on('adduser', function(username){
		// store the username in the socket session for this client
		socket.username = username;
		// store the room name in the socket session for this client
		socket.room = 'room1';
		// add the client's username to the global list
		usernames[username] = username;
		// send client to room 1
		socket.join('room1');
		// echo to client they've connected
		socket.emit('updatechat', 'SERVER', 'you have connected to room1');
		// echo to room 1 that a person has connected to their room
		socket.broadcast.to('room1').emit('updatechat', 'SERVER', username + ' has connected to this room');
		socket.emit('updaterooms', rooms, 'room1');
	});

	// when the client emits 'sendchat', this listens and executes
	socket.on('sendchat', function (data) {
		// we tell the client to execute 'updatechat' with 2 parameters
		io.sockets.in(socket.room).emit('updatechat', socket.username, data);
	});

	socket.on('switchRoom', function(newroom){
		// leave the current room (stored in session)
		socket.leave(socket.room);
		// join new room, received as function parameter
		socket.join(newroom);
		socket.emit('updatechat', 'SERVER', 'you have connected to '+ newroom);
		// sent message to OLD room
		socket.broadcast.to(socket.room).emit('updatechat', 'SERVER', socket.username+' has left this room');
		// update socket session room title
		socket.room = newroom;
		socket.broadcast.to(newroom).emit('updatechat', 'SERVER', socket.username+' has joined this room');
		socket.emit('updaterooms', rooms, newroom);
	});

	// when the user disconnects.. perform this
	socket.on('disconnect', function(){
		// remove the username from global usernames list
		delete usernames[socket.username];
		// update list of users in chat, client-side
		io.sockets.emit('updateusers', usernames);
		// echo globally that this client has left
		socket.broadcast.emit('updatechat', 'SERVER', socket.username + ' has disconnected');
		socket.leave(socket.room);
	});
});

here is the updated index.html:

<script src="/socket.io/socket.io.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<script>
	var socket = io.connect('http://localhost:8080');

	// on connection to server, ask for user's name with an anonymous callback
	socket.on('connect', function(){
		// call the server-side function 'adduser' and send one parameter (value of prompt)
		socket.emit('adduser', prompt("What's your name?"));
	});

	// listener, whenever the server emits 'updatechat', this updates the chat body
	socket.on('updatechat', function (username, data) {
		$('#conversation').append('<b>'+username + ':</b> ' + data + '<br>');
	});

	// listener, whenever the server emits 'updaterooms', this updates the room the client is in
	socket.on('updaterooms', function(rooms, current_room) {
		$('#rooms').empty();
		$.each(rooms, function(key, value) {
			if(value == current_room){
				$('#rooms').append('<div>' + value + '</div>');
			}
			else {
				$('#rooms').append('<div><a href="#" onclick="switchRoom(\''+value+'\')">' + value + '</a></div>');
			}
		});
	});

	function switchRoom(room){
		socket.emit('switchRoom', room);
	}

	// on load of page
	$(function(){
		// when the client clicks SEND
		$('#datasend').click( function() {
			var message = $('#data').val();
			$('#data').val('');
			// tell server to execute 'sendchat' and send along one parameter
			socket.emit('sendchat', message);
		});

		// when the client hits ENTER on their keyboard
		$('#data').keypress(function(e) {
			if(e.which == 13) {
				$(this).blur();
				$('#datasend').focus().click();
			}
		});
	});

</script>
<div style="float:left;width:100px;border-right:1px solid black;height:300px;padding:10px;overflow:scroll-y;">
	<b>ROOMS</b>
	<div id="rooms"></div>
</div>
<div style="float:left;width:300px;height:250px;overflow:scroll-y;padding:10px;">
	<div id="conversation"></div>
	<input id="data" style="width:200px;" />
	<input type="button" id="datasend" value="send" />
</div>

GIT repo https://github.com/mmukhin/psitsmike_example_2