Reconnecting-websocket NPM

Reconnecting WebSocket

WebSocket that will automatically reconnect if the connection is closed.

Features

WebSocket API compatible (same interface, Level0 and Level2 event model)
Fully configurable
Multi-platform (Web, ServiceWorkers, Node.js, React Native)
Dependency free (does not depend on Window, DOM or any EventEmitter library)
Handle connection timeouts
Allows changing server URL between reconnections
Buffering. Will send accumulated messages on open
Multiple builds available (see dist folder)
Debug mode

Install

npm install --save reconnecting-websocket

Usage

Compatible with WebSocket Browser API

So this documentation should be valid: MDN WebSocket API.

Ping me if you find any problems. Or, even better, write a test for your case and make a pull request :)

Simple usage

import ReconnectingWebSocket from 'reconnecting-websocket';

const rws = new ReconnectingWebSocket('ws://my.site.com');

rws.addEventListener('open', () => {
    rws.send('hello!');
});

Update URL

The url parameter will be resolved before connecting, possible types:

string
() => string
() => Promise<string>

import ReconnectingWebSocket from 'reconnecting-websocket';

const urls = ['ws://my.site.com', 'ws://your.site.com', 'ws://their.site.com'];
let urlIndex = 0;

// round robin url provider
const urlProvider = () => urls[urlIndex++ % urls.length];

const rws = new ReconnectingWebSocket(urlProvider);

import ReconnectingWebSocket from 'reconnecting-websocket';

// async url provider
const urlProvider = async () => {
    const token = await getSessionToken();
    return `wss://my.site.com/${token}`;
};

const rws = new ReconnectingWebSocket(urlProvider);

Options

Sample with custom options

import ReconnectingWebSocket from 'reconnecting-websocket';
import WS from 'ws';

const options = {
    WebSocket: WS, // custom WebSocket constructor
    connectionTimeout: 1000,
    maxRetries: 10,
};
const rws = new ReconnectingWebSocket('ws://my.site.com', [], options);

Available options

type Options = {
    WebSocket?: any; // WebSocket constructor, if none provided, defaults to global WebSocket
    maxReconnectionDelay?: number; // max delay in ms between reconnections
    minReconnectionDelay?: number; // min delay in ms between reconnections
    reconnectionDelayGrowFactor?: number; // how fast the reconnection delay grows
    minUptime?: number; // min time in ms to consider connection as stable
    connectionTimeout?: number; // retry connect if not connected after this time, in ms
    maxRetries?: number; // maximum number of retries
    maxEnqueuedMessages?: number; // maximum number of messages to buffer until reconnection
    startClosed?: boolean; // start websocket in CLOSED state, call `.reconnect()` to connect
    debug?: boolean; // enables debug output
};

Default values

WebSocket: undefined,
maxReconnectionDelay: 10000,
minReconnectionDelay: 1000 + Math.random() * 4000,
reconnectionDelayGrowFactor: 1.3,
minUptime: 5000,
connectionTimeout: 4000,
maxRetries: Infinity,
maxEnqueuedMessages: Infinity,
startClosed: false,
debug: false,

API

Methods

constructor(url: UrlProvider, protocols?: string | string[], options?: Options)

close(code?: number, reason?: string)
reconnect(code?: number, reason?: string)

send(data: string | ArrayBuffer | Blob | ArrayBufferView)

addEventListener(type: 'open' | 'close' | 'message' | 'error', listener: EventListener)
removeEventListener(type:  'open' | 'close' | 'message' | 'error', listener: EventListener)

Attributes

More info

binaryType: string;
bufferedAmount: number;
extensions: string;
onclose: EventListener;
onerror: EventListener;
onmessage: EventListener;
onopen: EventListener;
protocol: string;
readyState: number;
url: string;
retryCount: number;

Constants

CONNECTING 0 The connection is not yet open.
OPEN       1 The connection is open and ready to communicate.
CLOSING    2 The connection is in the process of closing.
CLOSED     3 The connection is closed or couldn't be opened.