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This document is a starter guide for migrating Socket.IO v0.6.x applications to Socket.IO v0.7.x.


Connecting to Socket.IO

In v0.6.x you would instantiate a socket and connect to it with something like:

var socket = new io.Socket(host, options);

In v0.7.x you should use io.connect, without new.

var socket = io.connect(uri, options);

In addition, you no longer need to pass port, host, secure. You simply pass a URL:

// connect at the same host / port as your website
var socket = io.connect();

// different port or host
var socket = io.connect('');

// secure
var socket = io.connect('https://localhost');

Flash SWF

You no longer need to set WEB_SOCKET_SWF_LOCATION global. It's always automatically loaded, as long as is being loaded correctly. You can still set it if you want to serve the .swf file from a different location.

Configuration options

Some configuration options changed names. Configuration options are passed as the second argument to io.connect.

connectTimeout 'connect timeout'
tryMultipleTransports 'try multiple transports'
reconnectionDelay 'reconnection delay'
maxReconnectionAttempts 'max reconnection attempts'

For example:

io.connect('http://localhost', { 'connect timeout': 5000 });


Listening on connections

To listen on events, you now listen on io.sockets instead of io:

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

We made this change because now supports multiple sockets (multiplexing) over the same connection:

io.of('/chat').on('connection', function (sockets) { });
io.of('/news').on('connection', function (sockets) { });

More information on the above can be found here.

Sending Data to Client

In v0.6, socket.send would automatically convert an object like { a: 'b' } to JSON. You would send data to a client with:

socket.send({ a: 'b' });

While this is cool, it poses a fundamental problem. JSON not only encodes objects, but also strings, numbers, etc! So, the API is more clear if you explicitly state you want to pass JSON (since there's a performance penalty associated with encoding/decoding JSON). In v0.7, use the json flag:

socket.json.send(data[, callback]);

Now you can also emit and receive custom events between the browser and server.

socket.emit('custom event'[, arguments][, callback]);
socket.on('custom event', callback);

Arguments for events get encoded in JSON automatically for you. More information on the above can be found here.

Broadcasting a message

In v0.7.0, if you want to send a message from a particular socket to the rest of the sockets, you can use the broadcast flag:

socket.broadcast.send('a message');
socket.broadcast.emit('a event'[, arguments]);

Sending a message to everyone

If you want to send a message to everyone you can reference io.sockets:


Session ID

If you made use of the sessionId property of socket in v0.6, this is now simply .id.

// v0.6.x
var sid = socket.sessionId;

// v0.7.x
var sid =;

sending messages to a client

// v0.6.x
socket.clients[sid].send({ a: 'b' });

// v0.7.x
io.sockets.sockets[sid].json.send({ a: 'b' });

Sending and emitting messages to a particular socket

io.sockets.socket(< session id>).send('my message')
io.sockets.socket(< session id>).emit('event name'[, arguments])
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