forever-websocket

WebSocket client, reconnecting and isomorphic. A simple implementation.

Features

• WebSocket API compatible.

  It exposes all properties and methods. API documentation is still valid: MDN WebSocket API for web browser and Node.js WebSocket for node.js

• Reconnecting, if connection drops

• Configurable reconnecting timers

• Configurable timeouts and reconnects when no message received

• Configurable pings to keep connection alive

• Allows changing URL and parameters between reconnections

Constructor

new ForeverWebSocket(address[, protocol][, options])

Parameters:

Name	Type	Attributes	Default	Description
address	string			The URL to which to connect
protocol	string | string[]	<optional>		The list of subprotocols
options	object	<optional>		Options1
options.automaticOpen	boolean	<optional>	true	Controls if WebSocket should be created and connected automatically to the server. See also connect()
options.reconnect	object | null	<optional>	{}	Parameters for reconnecting. Reconnection is enabled with default values when omitted. If null, no reconnection will reoccur
options.reconnect.strategy	'fibonacci' | 'exponential'	<optional>	'fibonacci'	Backoff strategy
options.reconnect.initialDelay	number	<optional>	50	Initial delay in milliseconds
options.reconnect.factor	number	<optional>	1.5	Multiplicative factor for 'exponential' backoff strategy
options.reconnect.maxDelay	number	<optional>	10000	Maximum delay in milliseconds
options.reconnect.randomizeDelay	boolean	<optional>	true	Whether to apply randomization (up to +20%) to the reconnection delay
options.timeout	number	<optional>	no timeout	Timeout in milliseconds after which the websockets reconnects when no messages are received
options.connectTimeout	number	<optional>	no connect timeout	Timeout in milliseconds for establishing the connection. If the connection is not open within this period, event connectTimeout is emitted, the pending connection is closed and a reconnect is attempted (if reconnection is enabled). When using node.js, the underlying ws handshakeTimeout option is passed through to the WebSocket as well
options.ping	object	<optional>	no ping	Controls how ping are sent to websocket server
options.ping.interval	number	<optional>		Ping interval value in milliseconds
options.ping.data	array | number | object | string | ArrayBuffer | buffer	<optional>		The data to send in the ping frame
options.ping.pingFrame	boolean	<optional>	false	Specifies whether ping should be sent as a ping frame. frame is accepted as an alias
options.ping.mask	boolean	<optional>		Specifies whether data should be masked or not
options.createWebSocket	function	<optional>		Functions which returns a WebSocket instance. If present it will be called when a new WebSocket is needed when reconnecting. The function could be useful in situations when the new WebSocket connection needs to be created with different parameters when reconnecting (e.g. a timestamp in the headers, or different URL)

Methods

All methods supported by WebSocket are supported, with unchanged behaviours and parameters. Exception are the methods below:

Method: connect()

Connects the WebSocket.

When ForeverWebsocket is created with automaticOpen = false in the constructor, underlying WebSocket objects is not created. In this case, method connect() needs to be used to create the WebSocket and connect it to the server.

The method has no effect if the WebSocket is already open, or if it is still being established (CONNECTING). Use refresh() to force a new connection.

Method: send(data)

Calls WebSocket send(). Parameter data can be an object, if so it is stringify'ed before it is sent.

Method: refresh(code, reason)

Calls Websocket close(). When event close is emitted, WebSocket is re-newed if reconnect option is active.

Method: close(code, reason)

Calls Websocket close(). Reconnection is not attempted.

Method: terminate()

Calls Websocket terminate(). Reconnection is not attempted.

Some WebSocket implementations do not support terminate(), in such case close() is called instead.

Method: updateOptions(options)

Selectively updates configuration options at runtime. Options for features which were not configured in the constructor are created on demand, so e.g. updateOptions({ timeout: 30000 }) enables the timeout, and updateOptions({ ping: { interval: 1000 } }) enables pings.

Passing null disables a feature: it stops and removes the corresponding manager. For timeout and connectTimeout, a non-positive value has the same effect as null.

Name	Type	Description
options.reconnect	object | null	Reconnection parameters. null disables reconnection
options.timeout	number | null	Inactivity timeout. null or 0 disables it
options.connectTimeout	number | null	Connect timeout. null or 0 disables it
options.ping	object | null	Ping parameters. null disables pings
options.createWebSocket	function	Custom WebSocket factory used when a new WebSocket is needed

Methods: addListener(eventName, listener) / removeListener(eventName, listener)

Aliases of on() and off() which also register the listener on the underlying WebSocket, so that it is attached again when the WebSocket is renewed at reconnect.

on(), once(), addEventListener(), off() and removeEventListener() behave the same way.

Events

All events normally emitted by WebSocket are emitted, with unchanged behaviour and parameters.

In addition, the following events are emitted:

Event: connecting

• retryNumber - The retry number
• lastConnectedMts - Millisecond timestamp on when WebSocket was last connected

It is emitted just before WebSocket tries to reconnect again.

Event: delay

• retryNumber - The retry number that will be attempted next
• delay - Period of delay in milliseconds until the next connection attempt

It is emitted when a connection attempt has failed and there needs to be a delay until the next retry.

Event: reconnected

• retryNumber - The number of retries needed to reconnect
• lastConnectedMts - Millisecond timestamp on when WebSocket was last connected

It is emitted when WebSocket is connected again.

WebSocket event open is still received. Event reconnected is an additional event which provides extra information.

Event: timeout

• lastRefreshMts - Millisecond timestamp when WebSocket connection was last refreshed, which is when connection was open or last message was received.

It is emitted when timout occurs. After the event is emitted the WebSocket connection is closed and a reconnect will be attempted if reconnection is configured.

Event: connectTimeout

It is emitted when the connection was not established within options.connectTimeout milliseconds. After the event is emitted the pending connection is closed and a reconnect will be attempted if reconnection is configured.

Footnotes

1. Standard WebSocket options are supported, in addition options described here are implemented ↩