418 lines
12 KiB
Markdown
418 lines
12 KiB
Markdown
# ws: a Node.js WebSocket library
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[](https://www.npmjs.com/package/ws)
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[](https://travis-ci.org/websockets/ws)
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[](https://ci.appveyor.com/project/lpinca/ws)
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[](https://coveralls.io/r/websockets/ws?branch=master)
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ws is a simple to use, blazing fast, and thoroughly tested WebSocket client
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and server implementation.
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Passes the quite extensive Autobahn test suite: [server][server-report],
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[client][client-report].
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**Note**: This module does not work in the browser. The client in the docs is a
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reference to a back end with the role of a client in the WebSocket
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communication. Browser clients must use the native
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[`WebSocket`](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket) object.
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To make the same code work seamlessly on Node.js and the browser, you can use
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one of the many wrappers available on npm, like
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[isomorphic-ws](https://github.com/heineiuo/isomorphic-ws).
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## Table of Contents
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* [Protocol support](#protocol-support)
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* [Installing](#installing)
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+ [Opt-in for performance and spec compliance](#opt-in-for-performance-and-spec-compliance)
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* [API docs](#api-docs)
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* [WebSocket compression](#websocket-compression)
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* [Usage examples](#usage-examples)
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+ [Sending and receiving text data](#sending-and-receiving-text-data)
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+ [Sending binary data](#sending-binary-data)
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+ [Simple server](#simple-server)
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+ [External HTTP/S server](#external-https-server)
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+ [Multiple servers sharing a single HTTP/S server](#multiple-servers-sharing-a-single-https-server)
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+ [Server broadcast](#server-broadcast)
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+ [echo.websocket.org demo](#echowebsocketorg-demo)
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+ [Other examples](#other-examples)
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* [Error handling best practices](#error-handling-best-practices)
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* [FAQ](#faq)
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+ [How to get the IP address of the client?](#how-to-get-the-ip-address-of-the-client)
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+ [How to detect and close broken connections?](#how-to-detect-and-close-broken-connections)
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+ [How to connect via a proxy?](#how-to-connect-via-a-proxy)
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* [Changelog](#changelog)
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* [License](#license)
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## Protocol support
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* **HyBi drafts 07-12** (Use the option `protocolVersion: 8`)
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* **HyBi drafts 13-17** (Current default, alternatively option `protocolVersion: 13`)
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## Installing
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```
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npm install --save ws
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```
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### Opt-in for performance and spec compliance
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There are 2 optional modules that can be installed along side with the ws
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module. These modules are binary addons which improve certain operations.
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Prebuilt binaries are available for the most popular platforms so you don't
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necessarily need to have a C++ compiler installed on your machine.
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- `npm install --save-optional bufferutil`: Allows to efficiently perform
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operations such as masking and unmasking the data payload of the WebSocket
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frames.
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- `npm install --save-optional utf-8-validate`: Allows to efficiently check
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if a message contains valid UTF-8 as required by the spec.
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## API docs
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See [`/doc/ws.md`](./doc/ws.md) for Node.js-like docs for the ws classes.
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## WebSocket compression
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ws supports the [permessage-deflate extension][permessage-deflate] which
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enables the client and server to negotiate a compression algorithm and its
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parameters, and then selectively apply it to the data payloads of each
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WebSocket message.
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The extension is disabled by default on the server and enabled by default on
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the client. It adds a significant overhead in terms of performance and memory
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consumption so we suggest to enable it only if it is really needed.
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Note that Node.js has a variety of issues with high-performance compression,
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where increased concurrency, especially on Linux, can lead to
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[catastrophic memory fragmentation][node-zlib-bug] and slow performance.
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If you intend to use permessage-deflate in production, it is worthwhile to set
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up a test representative of your workload and ensure Node.js/zlib will handle
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it with acceptable performance and memory usage.
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Tuning of permessage-deflate can be done via the options defined below. You can
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also use `zlibDeflateOptions` and `zlibInflateOptions`, which is passed directly
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into the creation of [raw deflate/inflate streams][node-zlib-deflaterawdocs].
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See [the docs][ws-server-options] for more options.
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```js
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const WebSocket = require('ws');
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const wss = new WebSocket.Server({
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port: 8080,
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perMessageDeflate: {
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zlibDeflateOptions: { // See zlib defaults.
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chunkSize: 1024,
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memLevel: 7,
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level: 3,
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},
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zlibInflateOptions: {
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chunkSize: 10 * 1024
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},
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// Other options settable:
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clientNoContextTakeover: true, // Defaults to negotiated value.
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serverNoContextTakeover: true, // Defaults to negotiated value.
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clientMaxWindowBits: 10, // Defaults to negotiated value.
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serverMaxWindowBits: 10, // Defaults to negotiated value.
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// Below options specified as default values.
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concurrencyLimit: 10, // Limits zlib concurrency for perf.
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threshold: 1024, // Size (in bytes) below which messages
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// should not be compressed.
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}
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});
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```
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The client will only use the extension if it is supported and enabled on the
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server. To always disable the extension on the client set the
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`perMessageDeflate` option to `false`.
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```js
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const WebSocket = require('ws');
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const ws = new WebSocket('ws://www.host.com/path', {
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perMessageDeflate: false
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});
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```
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## Usage examples
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### Sending and receiving text data
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```js
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const WebSocket = require('ws');
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const ws = new WebSocket('ws://www.host.com/path');
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ws.on('open', function open() {
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ws.send('something');
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});
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ws.on('message', function incoming(data) {
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console.log(data);
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});
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```
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### Sending binary data
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```js
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const WebSocket = require('ws');
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const ws = new WebSocket('ws://www.host.com/path');
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ws.on('open', function open() {
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const array = new Float32Array(5);
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for (var i = 0; i < array.length; ++i) {
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array[i] = i / 2;
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}
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ws.send(array);
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});
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```
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### Simple server
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```js
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const WebSocket = require('ws');
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const wss = new WebSocket.Server({ port: 8080 });
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wss.on('connection', function connection(ws) {
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ws.on('message', function incoming(message) {
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console.log('received: %s', message);
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});
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ws.send('something');
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});
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```
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### External HTTP/S server
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```js
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const fs = require('fs');
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const https = require('https');
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const WebSocket = require('ws');
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const server = new https.createServer({
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cert: fs.readFileSync('/path/to/cert.pem'),
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key: fs.readFileSync('/path/to/key.pem')
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});
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const wss = new WebSocket.Server({ server });
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wss.on('connection', function connection(ws) {
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ws.on('message', function incoming(message) {
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console.log('received: %s', message);
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});
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ws.send('something');
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});
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server.listen(8080);
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```
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### Multiple servers sharing a single HTTP/S server
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```js
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const http = require('http');
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const WebSocket = require('ws');
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const server = http.createServer();
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const wss1 = new WebSocket.Server({ noServer: true });
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const wss2 = new WebSocket.Server({ noServer: true });
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wss1.on('connection', function connection(ws) {
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// ...
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});
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wss2.on('connection', function connection(ws) {
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// ...
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});
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server.on('upgrade', function upgrade(request, socket, head) {
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const pathname = url.parse(request.url).pathname;
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if (pathname === '/foo') {
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wss1.handleUpgrade(request, socket, head, function done(ws) {
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wss1.emit('connection', ws, request);
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});
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} else if (pathname === '/bar') {
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wss2.handleUpgrade(request, socket, head, function done(ws) {
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wss2.emit('connection', ws, request);
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});
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} else {
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socket.destroy();
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}
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});
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server.listen(8080);
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```
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### Server broadcast
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```js
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const WebSocket = require('ws');
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const wss = new WebSocket.Server({ port: 8080 });
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// Broadcast to all.
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wss.broadcast = function broadcast(data) {
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wss.clients.forEach(function each(client) {
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if (client.readyState === WebSocket.OPEN) {
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client.send(data);
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}
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});
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};
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wss.on('connection', function connection(ws) {
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ws.on('message', function incoming(data) {
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// Broadcast to everyone else.
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wss.clients.forEach(function each(client) {
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if (client !== ws && client.readyState === WebSocket.OPEN) {
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client.send(data);
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}
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});
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});
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});
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```
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### echo.websocket.org demo
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```js
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const WebSocket = require('ws');
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const ws = new WebSocket('wss://echo.websocket.org/', {
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origin: 'https://websocket.org'
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});
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ws.on('open', function open() {
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console.log('connected');
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ws.send(Date.now());
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});
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ws.on('close', function close() {
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console.log('disconnected');
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});
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ws.on('message', function incoming(data) {
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console.log(`Roundtrip time: ${Date.now() - data} ms`);
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setTimeout(function timeout() {
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ws.send(Date.now());
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}, 500);
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});
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```
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### Other examples
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For a full example with a browser client communicating with a ws server, see the
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examples folder.
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Otherwise, see the test cases.
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## Error handling best practices
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```js
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// If the WebSocket is closed before the following send is attempted
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ws.send('something');
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// Errors (both immediate and async write errors) can be detected in an optional
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// callback. The callback is also the only way of being notified that data has
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// actually been sent.
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ws.send('something', function ack(error) {
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// If error is not defined, the send has been completed, otherwise the error
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// object will indicate what failed.
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});
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// Immediate errors can also be handled with `try...catch`, but **note** that
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// since sends are inherently asynchronous, socket write failures will *not* be
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// captured when this technique is used.
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try { ws.send('something'); }
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catch (e) { /* handle error */ }
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```
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## FAQ
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### How to get the IP address of the client?
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The remote IP address can be obtained from the raw socket.
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```js
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const WebSocket = require('ws');
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const wss = new WebSocket.Server({ port: 8080 });
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wss.on('connection', function connection(ws, req) {
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const ip = req.connection.remoteAddress;
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});
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```
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When the server runs behind a proxy like NGINX, the de-facto standard is to use
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the `X-Forwarded-For` header.
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```js
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wss.on('connection', function connection(ws, req) {
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const ip = req.headers['x-forwarded-for'].split(/\s*,\s*/)[0];
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});
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```
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### How to detect and close broken connections?
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Sometimes the link between the server and the client can be interrupted in a
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way that keeps both the server and the client unaware of the broken state of the
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connection (e.g. when pulling the cord).
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In these cases ping messages can be used as a means to verify that the remote
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endpoint is still responsive.
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```js
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const WebSocket = require('ws');
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const wss = new WebSocket.Server({ port: 8080 });
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function noop() {}
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function heartbeat() {
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this.isAlive = true;
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}
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wss.on('connection', function connection(ws) {
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ws.isAlive = true;
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ws.on('pong', heartbeat);
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});
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const interval = setInterval(function ping() {
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wss.clients.forEach(function each(ws) {
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if (ws.isAlive === false) return ws.terminate();
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ws.isAlive = false;
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ws.ping(noop);
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});
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}, 30000);
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```
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Pong messages are automatically sent in response to ping messages as required
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by the spec.
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### How to connect via a proxy?
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Use a custom `http.Agent` implementation like [https-proxy-agent][] or
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[socks-proxy-agent][].
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## Changelog
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We're using the GitHub [releases][changelog] for changelog entries.
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## License
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[MIT](LICENSE)
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[https-proxy-agent]: https://github.com/TooTallNate/node-https-proxy-agent
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[socks-proxy-agent]: https://github.com/TooTallNate/node-socks-proxy-agent
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[client-report]: http://websockets.github.io/ws/autobahn/clients/
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[server-report]: http://websockets.github.io/ws/autobahn/servers/
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[permessage-deflate]: https://tools.ietf.org/html/rfc7692
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[changelog]: https://github.com/websockets/ws/releases
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[node-zlib-bug]: https://github.com/nodejs/node/issues/8871
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[node-zlib-deflaterawdocs]: https://nodejs.org/api/zlib.html#zlib_zlib_createdeflateraw_options
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[ws-server-options]: https://github.com/websockets/ws/blob/master/doc/ws.md#new-websocketserveroptions-callback
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