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+# ws: a Node.js WebSocket library
+
+[![Version npm](https://img.shields.io/npm/v/ws.svg?logo=npm)](https://www.npmjs.com/package/ws)
+[![CI](https://img.shields.io/github/workflow/status/websockets/ws/CI/master?label=CI&logo=github)](https://github.com/websockets/ws/actions?query=workflow%3ACI+branch%3Amaster)
+[![Coverage Status](https://img.shields.io/coveralls/websockets/ws/master.svg?logo=coveralls)](https://coveralls.io/github/websockets/ws)
+
+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](#opt-in-for-performance)
+- [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)
+ - [Round-trip time](#round-trip-time)
+ - [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
+
+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.
+
+## 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
+import WebSocket, { WebSocketServer } from 'ws';
+
+const wss = new WebSocketServer({
+ 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 if context takeover is disabled.
+ }
+});
+```
+
+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
+import WebSocket from 'ws';
+
+const ws = new WebSocket('ws://www.host.com/path', {
+ perMessageDeflate: false
+});
+```
+
+## Usage examples
+
+### Sending and receiving text data
+
+```js
+import WebSocket from 'ws';
+
+const ws = new WebSocket('ws://www.host.com/path');
+
+ws.on('open', function open() {
+ ws.send('something');
+});
+
+ws.on('message', function message(data) {
+ console.log('received: %s', data);
+});
+```
+
+### Sending binary data
+
+```js
+import WebSocket from '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
+import { WebSocketServer } from 'ws';
+
+const wss = new WebSocketServer({ port: 8080 });
+
+wss.on('connection', function connection(ws) {
+ ws.on('message', function message(data) {
+ console.log('received: %s', data);
+ });
+
+ ws.send('something');
+});
+```
+
+### External HTTP/S server
+
+```js
+import { createServer } from 'https';
+import { readFileSync } from 'fs';
+import { WebSocketServer } from 'ws';
+
+const server = createServer({
+ cert: readFileSync('/path/to/cert.pem'),
+ key: readFileSync('/path/to/key.pem')
+});
+const wss = new WebSocketServer({ server });
+
+wss.on('connection', function connection(ws) {
+ ws.on('message', function message(data) {
+ console.log('received: %s', data);
+ });
+
+ ws.send('something');
+});
+
+server.listen(8080);
+```
+
+### Multiple servers sharing a single HTTP/S server
+
+```js
+import { createServer } from 'http';
+import { parse } from 'url';
+import { WebSocketServer } from 'ws';
+
+const server = createServer();
+const wss1 = new WebSocketServer({ noServer: true });
+const wss2 = new WebSocketServer({ noServer: true });
+
+wss1.on('connection', function connection(ws) {
+ // ...
+});
+
+wss2.on('connection', function connection(ws) {
+ // ...
+});
+
+server.on('upgrade', function upgrade(request, socket, head) {
+ const { pathname } = parse(request.url);
+
+ 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
+import WebSocket from 'ws';
+import { createServer } from 'http';
+
+const server = createServer();
+const wss = new WebSocketServer({ noServer: true });
+
+wss.on('connection', function connection(ws, request, client) {
+ ws.on('message', function message(data) {
+ console.log(`Received message ${data} from user ${client}`);
+ });
+});
+
+server.on('upgrade', function upgrade(request, socket, head) {
+ // This function is not defined on purpose. Implement it with your own logic.
+ authenticate(request, function next(err, client) {
+ if (err || !client) {
+ socket.write('HTTP/1.1 401 Unauthorized\r\n\r\n');
+ socket.destroy();
+ return;
+ }
+
+ wss.handleUpgrade(request, socket, head, function done(ws) {
+ wss.emit('connection', ws, request, client);
+ });
+ });
+});
+
+server.listen(8080);
+```
+
+Also see the provided [example][session-parse-example] using `express-session`.
+
+### Server broadcast
+
+A client WebSocket broadcasting to all connected WebSocket clients, including
+itself.
+
+```js
+import WebSocket, { WebSocketServer } from 'ws';
+
+const wss = new WebSocketServer({ port: 8080 });
+
+wss.on('connection', function connection(ws) {
+ ws.on('message', function message(data, isBinary) {
+ wss.clients.forEach(function each(client) {
+ if (client.readyState === WebSocket.OPEN) {
+ client.send(data, { binary: isBinary });
+ }
+ });
+ });
+});
+```
+
+A client WebSocket broadcasting to every other connected WebSocket clients,
+excluding itself.
+
+```js
+import WebSocket, { WebSocketServer } from 'ws';
+
+const wss = new WebSocketServer({ port: 8080 });
+
+wss.on('connection', function connection(ws) {
+ ws.on('message', function message(data, isBinary) {
+ wss.clients.forEach(function each(client) {
+ if (client !== ws && client.readyState === WebSocket.OPEN) {
+ client.send(data, { binary: isBinary });
+ }
+ });
+ });
+});
+```
+
+### Round-trip time
+
+```js
+import WebSocket from 'ws';
+
+const ws = new WebSocket('wss://websocket-echo.com/');
+
+ws.on('open', function open() {
+ console.log('connected');
+ ws.send(Date.now());
+});
+
+ws.on('close', function close() {
+ console.log('disconnected');
+});
+
+ws.on('message', function message(data) {
+ console.log(`Round-trip time: ${Date.now() - data} ms`);
+
+ setTimeout(function timeout() {
+ ws.send(Date.now());
+ }, 500);
+});
+```
+
+### Use the Node.js streams API
+
+```js
+import WebSocket, { createWebSocketStream } from 'ws';
+
+const ws = new WebSocket('wss://websocket-echo.com/');
+
+const duplex = createWebSocketStream(ws, { encoding: 'utf8' });
+
+duplex.pipe(process.stdout);
+process.stdin.pipe(duplex);
+```
+
+### Other examples
+
+For a full example with a browser client communicating with a ws server, see the
+examples folder.
+
+Otherwise, see the test cases.
+
+## FAQ
+
+### How to get the IP address of the client?
+
+The remote IP address can be obtained from the raw socket.
+
+```js
+import { WebSocketServer } from 'ws';
+
+const wss = new WebSocketServer({ port: 8080 });
+
+wss.on('connection', function connection(ws, req) {
+ const ip = req.socket.remoteAddress;
+});
+```
+
+When the server runs behind a proxy like NGINX, the de-facto standard is to use
+the `X-Forwarded-For` header.
+
+```js
+wss.on('connection', function connection(ws, req) {
+ const ip = req.headers['x-forwarded-for'].split(',')[0].trim();
+});
+```
+
+### How to detect and close broken connections?
+
+Sometimes the link between the server and the client can be interrupted in a way
+that keeps both the server and the client unaware of the broken state of the
+connection (e.g. when pulling the cord).
+
+In these cases ping messages can be used as a means to verify that the remote
+endpoint is still responsive.
+
+```js
+import { WebSocketServer } from 'ws';
+
+function heartbeat() {
+ this.isAlive = true;
+}
+
+const wss = new WebSocketServer({ port: 8080 });
+
+wss.on('connection', function connection(ws) {
+ ws.isAlive = true;
+ ws.on('pong', heartbeat);
+});
+
+const interval = setInterval(function ping() {
+ wss.clients.forEach(function each(ws) {
+ if (ws.isAlive === false) return ws.terminate();
+
+ ws.isAlive = false;
+ ws.ping();
+ });
+}, 30000);
+
+wss.on('close', function close() {
+ clearInterval(interval);
+});
+```
+
+Pong messages are automatically sent in response to ping messages as required by
+the spec.
+
+Just like the server example above your clients might as well lose connection
+without knowing it. You might want to add a ping listener on your clients to
+prevent that. A simple implementation would be:
+
+```js
+import WebSocket from 'ws';
+
+function heartbeat() {
+ clearTimeout(this.pingTimeout);
+
+ // Use `WebSocket#terminate()`, which immediately destroys the connection,
+ // instead of `WebSocket#close()`, which waits for the close timer.
+ // Delay should be equal to the interval at which your server
+ // sends out pings plus a conservative assumption of the latency.
+ this.pingTimeout = setTimeout(() => {
+ this.terminate();
+ }, 30000 + 1000);
+}
+
+const client = new WebSocket('wss://websocket-echo.com/');
+
+client.on('open', heartbeat);
+client.on('ping', heartbeat);
+client.on('close', function clear() {
+ clearTimeout(this.pingTimeout);
+});
+```
+
+### How to connect via a proxy?
+
+Use a custom `http.Agent` implementation like [https-proxy-agent][] or
+[socks-proxy-agent][].
+
+## Changelog
+
+We're using the GitHub [releases][changelog] for changelog entries.
+
+## License
+
+[MIT](LICENSE)
+
+[changelog]: https://github.com/websockets/ws/releases
+[client-report]: http://websockets.github.io/ws/autobahn/clients/
+[https-proxy-agent]: https://github.com/TooTallNate/node-https-proxy-agent
+[node-zlib-bug]: https://github.com/nodejs/node/issues/8871
+[node-zlib-deflaterawdocs]:
+ https://nodejs.org/api/zlib.html#zlib_zlib_createdeflateraw_options
+[permessage-deflate]: https://tools.ietf.org/html/rfc7692
+[server-report]: http://websockets.github.io/ws/autobahn/servers/
+[session-parse-example]: ./examples/express-session-parse
+[socks-proxy-agent]: https://github.com/TooTallNate/node-socks-proxy-agent
+[ws-server-options]:
+ https://github.com/websockets/ws/blob/master/doc/ws.md#new-websocketserveroptions-callback