# ws: a Node.js WebSocket library
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ws is a simple to use, blazing fast, and thoroughly tested WebSocket client and
server implementation.
Passes the quite extensive Autobahn test suite: [server][server-report],
[client][client-report].
**Note**: This module does not work in the browser. The client in the docs is a
reference to a back end with the role of a client in the WebSocket
communication. Browser clients must use the native
[`WebSocket`](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket)
object. To make the same code work seamlessly on Node.js and the browser, you
can use one of the many wrappers available on npm, like
[isomorphic-ws](https://github.com/heineiuo/isomorphic-ws).
## Table of Contents
- [Protocol support](#protocol-support)
- [Installing](#installing)
- [Opt-in for performance and spec compliance](#opt-in-for-performance-and-spec-compliance)
- [API docs](#api-docs)
- [WebSocket compression](#websocket-compression)
- [Usage examples](#usage-examples)
- [Sending and receiving text data](#sending-and-receiving-text-data)
- [Sending binary data](#sending-binary-data)
- [Simple server](#simple-server)
- [External HTTP/S server](#external-https-server)
- [Multiple servers sharing a single HTTP/S server](#multiple-servers-sharing-a-single-https-server)
- [Client authentication](#client-authentication)
- [Server broadcast](#server-broadcast)
- [echo.websocket.org demo](#echowebsocketorg-demo)
- [Use the Node.js streams API](#use-the-nodejs-streams-api)
- [Other examples](#other-examples)
- [FAQ](#faq)
- [How to get the IP address of the client?](#how-to-get-the-ip-address-of-the-client)
- [How to detect and close broken connections?](#how-to-detect-and-close-broken-connections)
- [How to connect via a proxy?](#how-to-connect-via-a-proxy)
- [Changelog](#changelog)
- [License](#license)
## Protocol support
- **HyBi drafts 07-12** (Use the option `protocolVersion: 8`)
- **HyBi drafts 13-17** (Current default, alternatively option
`protocolVersion: 13`)
## Installing
```
npm install ws
```
### Opt-in for performance and spec compliance
There are 2 optional modules that can be installed along side with the ws
module. These modules are binary addons which improve certain operations.
Prebuilt binaries are available for the most popular platforms so you don't
necessarily need to have a C++ compiler installed on your machine.
- `npm install --save-optional bufferutil`: Allows to efficiently perform
operations such as masking and unmasking the data payload of the WebSocket
frames.
- `npm install --save-optional utf-8-validate`: Allows to efficiently check if a
message contains valid UTF-8 as required by the spec.
## API docs
See [`/doc/ws.md`](./doc/ws.md) for Node.js-like documentation of ws classes and
utility functions.
## WebSocket compression
ws supports the [permessage-deflate extension][permessage-deflate] which enables
the client and server to negotiate a compression algorithm and its parameters,
and then selectively apply it to the data payloads of each WebSocket message.
The extension is disabled by default on the server and enabled by default on the
client. It adds a significant overhead in terms of performance and memory
consumption so we suggest to enable it only if it is really needed.
Note that Node.js has a variety of issues with high-performance compression,
where increased concurrency, especially on Linux, can lead to [catastrophic
memory fragmentation][node-zlib-bug] and slow performance. If you intend to use
permessage-deflate in production, it is worthwhile to set up a test
representative of your workload and ensure Node.js/zlib will handle it with
acceptable performance and memory usage.
Tuning of permessage-deflate can be done via the options defined below. You can
also use `zlibDeflateOptions` and `zlibInflateOptions`, which is passed directly
into the creation of [raw deflate/inflate streams][node-zlib-deflaterawdocs].
See [the docs][ws-server-options] for more options.
```js
const WebSocket = require('ws');
const wss = new WebSocket.Server({
port: 8080,
perMessageDeflate: {
zlibDeflateOptions: {
// See zlib defaults.
chunkSize: 1024,
memLevel: 7,
level: 3
},
zlibInflateOptions: {
chunkSize: 10 * 1024
},
// Other options settable:
clientNoContextTakeover: true, // Defaults to negotiated value.
serverNoContextTakeover: true, // Defaults to negotiated value.
serverMaxWindowBits: 10, // Defaults to negotiated value.
// Below options specified as default values.
concurrencyLimit: 10, // Limits zlib concurrency for perf.
threshold: 1024 // Size (in bytes) below which messages
// should not be compressed.
}
});
```
The client will only use the extension if it is supported and enabled on the
server. To always disable the extension on the client set the
`perMessageDeflate` option to `false`.
```js
const WebSocket = require('ws');
const ws = new WebSocket('ws://www.host.com/path', {
perMessageDeflate: false
});
```
## Usage examples
### Sending and receiving text data
```js
const WebSocket = require('ws');
const ws = new WebSocket('ws://www.host.com/path');
ws.on('open', function open() {
ws.send('something');
});
ws.on('message', function incoming(data) {
console.log(data);
});
```
### Sending binary data
```js
const WebSocket = require('ws');
const ws = new WebSocket('ws://www.host.com/path');
ws.on('open', function open() {
const array = new Float32Array(5);
for (var i = 0; i < array.length; ++i) {
array[i] = i / 2;
}
ws.send(array);
});
```
### Simple server
```js
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });
wss.on('connection', function connection(ws) {
ws.on('message', function incoming(message) {
console.log('received: %s', message);
});
ws.send('something');
});
```
### External HTTP/S server
```js
const fs = require('fs');
const https = require('https');
const WebSocket = require('ws');
const server = https.createServer({
cert: fs.readFileSync('/path/to/cert.pem'),
key: fs.readFileSync('/path/to/key.pem')
});
const wss = new WebSocket.Server({ server });
wss.on('connection', function connection(ws) {
ws.on('message', function incoming(message) {
console.log('received: %s', message);
});
ws.send('something');
});
server.listen(8080);
```
### Multiple servers sharing a single HTTP/S server
```js
const http = require('http');
const WebSocket = require('ws');
const url = require('url');
const server = http.createServer();
const wss1 = new WebSocket.Server({ noServer: true });
const wss2 = new WebSocket.Server({ noServer: true });
wss1.on('connection', function connection(ws) {
// ...
});
wss2.on('connection', function connection(ws) {
// ...
});
server.on('upgrade', function upgrade(request, socket, head) {
const pathname = url.parse(request.url).pathname;
if (pathname === '/foo') {
wss1.handleUpgrade(request, socket, head, function done(ws) {
wss1.emit('connection', ws, request);
});
} else if (pathname === '/bar') {
wss2.handleUpgrade(request, socket, head, function done(ws) {
wss2.emit('connection', ws, request);
});
} else {
socket.destroy();
}
});
server.listen(8080);
```
### Client authentication
```js
const http = require('http');
const WebSocket = require('ws');
const server = http.createServer();
const wss = new WebSocket.Server({ noServer: true