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# socket.io [![Build Status](https://secure.travis-ci.org/socketio/socket.io.svg)](https://travis-ci.org/socketio/socket.io) [![Dependency Status](https://david-dm.org/socketio/socket.io.svg)](https://david-dm.org/socketio/socket.io) [![devDependency Status](https://david-dm.org/socketio/socket.io/dev-status.svg)](https://david-dm.org/socketio/socket.io#info=devDependencies) ![NPM version](https://badge.fury.io/js/socket.io.svg) ![Downloads](https://img.shields.io/npm/dm/socket.io.svg?style=flat) [![](http://slack.socket.io/badge.svg?)](http://slack.socket.io) ## How to use The following example attaches socket.io to a plain Node.JS HTTP server listening on port `3000`. ```js var server = require('http').createServer(); var io = require('socket.io')(server); io.on('connection', function(socket){ socket.on('event', function(data){}); socket.on('disconnect', function(){}); }); server.listen(3000); ``` ### Standalone ```js var io = require('socket.io')(); io.on('connection', function(socket){}); io.listen(3000); ``` ### In conjunction with Express Starting with **3.0**, express applications have become request handler functions that you pass to `http` or `http` `Server` instances. You need to pass the `Server` to `socket.io`, and not the express application function. ```js var app = require('express')(); var server = require('http').createServer(app); var io = require('socket.io')(server); io.on('connection', function(){ /* … */ }); server.listen(3000); ``` ### In conjunction with Koa Like Express.JS, Koa works by exposing an application as a request handler function, but only by calling the `callback` method. ```js var app = require('koa')(); var server = require('http').createServer(app.callback()); var io = require('socket.io')(server); io.on('connection', function(){ /* … */ }); server.listen(3000); ``` ## API ### Server Exposed by `require('socket.io')`. ### Server() Creates a new `Server`. Works with and without `new`: ```js var io = require('socket.io')(); // or var Server = require('socket.io'); var io = new Server(); ``` ### Server(opts:Object) Optionally, the first or second argument (see below) of the `Server` constructor can be an options object. The following options are supported: - `serveClient` sets the value for Server#serveClient() - `path` sets the value for Server#path() The same options passed to socket.io are always passed to the `engine.io` `Server` that gets created. See engine.io [options](https://github.com/socketio/engine.io#methods-1) as reference. ### Server(srv:http#Server, opts:Object) Creates a new `Server` and attaches it to the given `srv`. Optionally `opts` can be passed. ### Server(port:Number, opts:Object) Binds socket.io to a new `http.Server` that listens on `port`. ### Server#serveClient(v:Boolean):Server If `v` is `true` the attached server (see `Server#attach`) will serve the client files. Defaults to `true`. This method has no effect after `attach` is called. ```js // pass a server and the `serveClient` option var io = require('socket.io')(http, { serveClient: false }); // or pass no server and then you can call the method var io = require('socket.io')(); io.serveClient(false); io.attach(http); ``` If no arguments are supplied this method returns the current value. ### Server#path(v:String):Server Sets the path `v` under which `engine.io` and the static files will be served. Defaults to `/socket.io`. If no arguments are supplied this method returns the current value. ### Server#adapter(v:Adapter):Server Sets the adapter `v`. Defaults to an instance of the `Adapter` that ships with socket.io which is memory based. See [socket.io-adapter](https://github.com/socketio/socket.io-adapter). If no arguments are supplied this method returns the current value. ### Server#origins(v:String):Server Sets the allowed origins `v`. Defaults to any origins being allowed. If no arguments are supplied this method returns the current value. ### Server#origins(v:Function):Server Sets the allowed origins as dynamic function. Function takes two arguments `origin:String` and `callback(error, success)`, where `success` is a boolean value indicating whether origin is allowed or not. __Potential drawbacks__: * in some situations, when it is not possible to determine `origin` it may have value of `*` * As this function will be executed for every request, it is advised to make this function work as fast as possible * If `socket.io` is used together with `Express`, the CORS headers will be affected only for `socket.io` requests. For Express can use [cors](https://github.com/expressjs/cors) ### Server#sockets:Namespace The default (`/`) namespace. ### Server#attach(srv:http#Server, opts:Object):Server Attaches the `Server` to an engine.io instance on `srv` with the supplied `opts` (optionally). ### Server#attach(port:Number, opts:Object):Server Attaches the `Server` to an engine.io instance that is bound to `port` with the given `opts` (optionally). ### Server#listen Synonym of `Server#attach`. ### Server#bind(srv:engine#Server):Server Advanced use only. Binds the server to a specific engine.io `Server` (or compatible API) instance. ### Server#onconnection(socket:engine#Socket):Server Advanced use only. Creates a new `socket.io` client from the incoming engine.io (or compatible API) `socket`. ### Server#of(nsp:String):Namespace Initializes and retrieves the given `Namespace` by its pathname identifier `nsp`. If the namespace was already initialized it returns it right away. ### Server#emit Emits an event to all connected clients. The following two are equivalent: ```js var io = require('socket.io')(); io.sockets.emit('an event sent to all connected clients'); io.emit('an event sent to all connected clients'); ``` For other available methods, see `Namespace` below. ### Server#close Closes socket server ```js var Server = require('socket.io'); var PORT = 3030; var server = require('http').Server(); var io = Server(PORT); io.close(); // Close current server server.listen(PORT); // PORT is free to use io = Server(server); ``` ### Server#use See `Namespace#use` below. ### Namespace Represents a pool of sockets connected under a given scope identified by a pathname (eg: `/chat`). By default the client always connects to `/`. #### Events - `connection` / `connect`. Fired upon a connection. Parameters: - `Socket` the incoming socket. ### Namespace#name:String The namespace identifier property. ### Namespace#connected:Object<Socket> Hash of `Socket` objects that are connected to this namespace indexed by `id`. ### Namespace#clients(fn:Function) Gets a list of client IDs connected to this namespace (across all nodes if applicable). An example to get all clients in a namespace: ```js var io = require('socket.io')(); io.of('/chat').clients(function(error, clients){ if (error) throw error; console.log(clients); // => [PZDoMHjiu8PYfRiKAAAF, Anw2LatarvGVVXEIAAAD] }); ``` An example to get all clients in namespace's room: ```js var io = require('socket.io')(); io.of('/chat').in('general').clients(function(error, clients){ if (error) throw error; console.log(clients); // => [Anw2LatarvGVVXEIAAAD] }); ``` As with broadcasting, the default is all clients from the default namespace ('/'): ```js var io = require('socket.io')(); io.clients(function(error, clients){ if (error) throw error; console.log(clients); // => [6em3d4TJP8Et9EMNAAAA, G5p55dHhGgUnLUctAAAB] }); ``` ### Namespace#use(fn:Function):Namespace Registers a middleware, which is a function that gets executed for every incoming `Socket` and receives as parameter the socket and a function to optionally defer execution to the next registered middleware. ```js var io = require('socket.io')(); io.use(function(socket, next){ if (socket.request.headers.cookie) return next(); next(new Error('Authentication error')); }); ``` Errors passed to middleware callbacks are sent as special `error` packets to clients. ### Socket A `Socket` is the fundamental class for interacting with browser clients. A `Socket` belongs to a certain `Namespace` (by default `/`) and uses an underlying `Client` to communicate. ### Socket#rooms:Object A hash of strings identifying the rooms this socket is in, indexed by room name. ### Socket#client:Client A reference to the underlying `Client` object. ### Socket#conn:Socket A reference to the underlying `Client` transport connection (engine.io `Socket` object). ### Socket#request:Request A getter proxy that returns the reference to the `request` that originated the underlying engine.io `Client`. Useful for accessing request headers such as `Cookie` or `User-Agent`. ### Socket#id:String A unique identifier for the socket session, that comes from the underlying `Client`. ### Socket#emit(name:String[, …]):Socket Emits an event to the socket identified by the string `name`. Any other parameters can be included. All datastructures are supported, including `Buffer`. JavaScript functions can't be serialized/deserialized. ```js var io = require('socket.io')(); io.on('connection', function(socket){ socket.emit('an event', { some: 'data' }); }); ``` ### Socket#join(name:String[, fn:Function]):Socket Adds the socket to the `room`, and fires optionally a callback `fn` with `err` signature (if any). The socket is automatically a member of a room identified with its session id (see `Socket#id`). The mechanics of joining rooms are handled by the `Adapter` that has been configured (see `Server#adapter` above), defaulting to [socket.io-adapter](https://github.com/socketio/socket.io-adapter). ### Socket#leave(name:String[, fn:Function]):Socket Removes the socket from `room`, and fires optionally a callback `fn` with `err` signature (if any). **Rooms are left automatically upon disconnection**. The mechanics of leaving rooms are handled by the `Adapter` that has been configured (see `Server#adapter` above), defaulting to [socket.io-adapter](https://github.com/socketio/socket.io-adapter). ### Socket#to(room:String):Socket Sets a modifier for a subsequent event emission that the event will only be _broadcasted_ to sockets that have joined the given `room`. To emit to multiple rooms, you can call `to` several times. ```js var io = require('socket.io')(); io.on('connection', function(socket){ socket.to('others').emit('an event', { some: 'data' }); }); ``` ### Socket#in(room:String):Socket Same as `Socket#to` ### Socket#compress(v:Boolean):Socket Sets a modifier for a subsequent event emission that the event data will only be _compressed_ if the value is `true`. Defaults to `true` when you don't call the method. ```js var io = require('socket.io')(); io.on('connection', function(socket){ socket.compress(false).emit('an event', { some: 'data' }); }); ``` ### Client The `Client` class represents an incoming transport (engine.io) connection. A `Client` can be associated with many multiplexed `Socket` that belong to different `Namespace`s. ### Client#conn A reference to the underlying `engine.io` `Socket` connection. ### Client#request A getter proxy that returns the reference to the `request` that originated the engine.io connection. Useful for accessing request headers such as `Cookie` or `User-Agent`. ## Debug / logging Socket.IO is powered by [debug](https://github.com/visionmedia/debug). In order to see all the debug output, run your app with the environment variable `DEBUG` including the desired scope. To see the output from all of Socket.IO's debugging scopes you can use: ``` DEBUG=socket.io* node myapp ``` ## License MIT |