ReconnectingWebSocket

A small JavaScript library that decorates the WebSocket API to provide a WebSocket connection that will automatically reconnect if the connection is dropped.

It is API compatible, so when you have:

var ws = new WebSocket('ws://....');

you can replace with:

var ws = new ReconnectingWebSocket('ws://....');

Minified library with gzip compression is less than 600 bytes.

How reconnections occur

With the standard WebSocket API, the events you receive from the WebSocket instance are typically:

onopen
onmessage
onmessage
onmessage
onclose // At this point the WebSocket instance is dead.

With a ReconnectingWebSocket, after an onclose event is called it will automatically attempt to reconnect. In addition, a connection is attempted repeatedly (with a small pause) until it succeeds. So the events you receive may look something more like:

onopen
onmessage
onmessage
onmessage
onclose
// ReconnectingWebSocket attempts to reconnect
onopen
onmessage
onmessage
onmessage
onclose
// ReconnectingWebSocket attempts to reconnect
onopen
onmessage
onmessage
onmessage
onclose

This is all handled automatically for you by the library.

Parameters

var socket = new ReconnectingWebSocket(url, protocols, options);

`url`

The URL you are connecting to.
https://html.spec.whatwg.org/multipage/comms.html#network

`protocols`

Optional string or array of protocols per the WebSocket spec.
https://tools.ietf.org/html/rfc6455

`options`

Options (see below)

Options

Options can either be passed as the 3rd parameter upon instantiation or set directly on the object after instantiation:

var socket = new ReconnectingWebSocket(url, null, {debug: true, reconnectInterval: 3000});

or

var socket = new ReconnectingWebSocket(url);
socket.debug = true;
socket.timeoutInterval = 5400;

`debug`

Whether this instance should log debug messages or not. Debug messages are printed to console.debug().
Accepts true or false
Default value: false

`automaticOpen`

Whether or not the websocket should attempt to connect immediately upon instantiation. The socket can be manually opened or closed at any time using ws.open() and ws.close().
Accepts true or false
Default value: true

`reconnectInterval`

The number of milliseconds to delay before attempting to reconnect.
Accepts integer
Default: 1000

`maxReconnectInterval`

The maximum number of milliseconds to delay a reconnection attempt.
Accepts integer
Default: 30000

####reconnectDecay

The rate of increase of the reconnect delay. Allows reconnect attempts to back off when problems persist.
Accepts integer or float
Default: 1.5

`timeoutInterval`

The maximum time in milliseconds to wait for a connection to succeed before closing and retrying.
Accepts integer
Default: 2000

`maxReconnectAttempts`

The maximum number of reconnection attempts that will be made before giving up. If null, reconnection attempts will be continue to be made forever.
Accepts integer or null.
Default: null

`binaryType`

The binary type is required by some applications.
Accepts strings 'blob' or 'arraybuffer'.
Default: 'blob'

Methods

`ws.open()`

Open the Reconnecting Websocket

`ws.close(code, reason)`

Closes the WebSocket connection or connection attempt, if any. If the connection is already CLOSED, this method does nothing.
code is optional the closing code (default value 1000). https://tools.ietf.org/html/rfc6455#section-7.4.1
reason is the optional reason that the socket is being closed. https://tools.ietf.org/html/rfc6455#section-7.1.6

`ws.refresh()`

Refresh the connection if still open (close and then re-open it).

`ws.send(data)`

Transmits data to the server over the WebSocket connection.
Accepts @param data a text string, ArrayBuffer or Blob

Like this? Check out websocketd for the simplest way to create WebSocket backends from any programming language.

Follow @joewalnes

License

theeuwes-it/reconnecting-websocket

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