Migration from 0.9

For most applications, the transition to 1.0 should be completely seamless and devoid of any hiccups. That said, we’ve done some work to streamline some APIs, and we have changed some internals, so this is a recommended read for most existing users.

Authentication differences

Socket.io uses middleware now

You can give a Socket.io server arbitrary functions via io.use() that are run when a socket is created. Check out this example:

var srv = require('http').createServer();
var io = require('socket.io')(srv);
var run = 0;
io.use(function(socket, next){
  run++; // 0 -> 1
io.use(function(socket, next) {
  run++; // 1 -> 2
var socket = require('socket.io-client')();
socket.on('connect', function(){
  // run == 2 at this time

… so its cleaner to do auth via middleware now

The old io.set() and io.get() methods are deprecated and only supported for backwards compatibility. Here is a translation of an old authorization example into middleware-style.

io.set('authorization', function (handshakeData, callback) {
  // make sure the handshake data looks good
  callback(null, true); // error first, 'authorized' boolean second 


io.use(function(socket, next) {
  var handshakeData = socket.request;
  // make sure the handshake data looks good as before
  // if error do this:
    // next(new Error('not authorized');
  // else just call next

Namespace authorization?

io.of('/namespace').use(function(socket, next) {
  var handshakeData = socket.request;

Log differences

Logging is now based on debug

To print all debug logging, set the environment variable DEBUG to *. ie: DEBUG=* node index.js

To print only socket.io related logging: DEBUG=socket.io:* node index.js.

To print logging only from the socket object: DEBUG=socket.io:socket node index.js.

This pattern should hopefully be making sense at this point. The names of the files in socket.io/lib are equivalent to their debug names.

Debug also works in the browser; logs are persisted to localstorage. To use: open the developer console and type localStorage.debug = 'socket.io:*' (or any debug level) and then refresh the page. Everything is logged until you run localStorage.debug = ''

See more at the debug documentation here.


In general there are some new shortcuts for common things. The old versions should still work, but shortcuts are nice.

Broadcasting to all clients in default namespace


io.sockets.emit('eventname', 'eventdata');


io.emit('eventname', 'eventdata');

Neat. Note that in both cases, these messages reach all clients connected to the default ‘/’ namespace, but not clients in other namespaces.

Starting the server


var io = require('socket.io');
var socket = io.listen(80, { /* options */ });


var io = require('socket.io');
var socket = io({ /* options */ });

Configuration differences

io.set is gone

Instead do configuration in server initialization like this:

var socket = require('socket.io')({
  // options go here

Options like log-level are gone. io.set('transports'), io.set('heartbeat interval'), io.set('heartbeat timeout', and io.set('resource') are still supported for backwards compatibility.

Setting resource path

The previous resource option is equivalent to the new path option, but needs a / in the beginning. For example, the following configuration

var socket = io.connect('localhost:3000', {
  'resource': 'path/to/socket.io';


var socket = io.connect('localhost:3000', {
  'path': '/path/to/socket.io';

Parser / Protocol differences

This is only relevant for updating things like socket.io implementations in other languages, custom socket.io clients, etc.

Difference 1 – packet encoding

Parsing is now class based and asynchronous. Instead of returning a single encoded string, encode calls callback with an array of encodings as the only argument. Each encoding should be written to the transport in order. This is more flexible and makes binary data transport work. Here’s an example:

var encoding = parser.encode(packet);
console.log(encoding); // fully encoded packet


var encoder = new parser.Encoder();
encoder.encode(packet, function(encodings) {
  for (var i = 0; i < encodings.length; i++) {
    console.log(encodings[i]); // encoded parts of the packet

Difference 2 – packet decoding

Decoding takes things a step further and is event-based. This is done because some objects (binary-containing) are both encoded and decoded in multiple parts. This example should help:

var packet = parser.decode(decoding);
console.log(packet); // formed socket.io packet to handle


var decoder = new parser.Decoder();
decoder.on('decoded', function(packet) {
  console.log(packet); // formed socket.io packet to handle
decoder.add(encodings[0]); // say encodings is array of two encodings received from transport
decoder.add(encodings[1]); // after adding the last element, 'decoded' is emitted from decoder

© 2014–2015 Automattic
Licensed under the MIT License.