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. 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	number	<optional>	0	Range of randomness and must be between 0 and 1
options.timeout	number	<optional>	no timeout	Timeout in milliseconds after which the websockets reconnects when no messages are received
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
options.ping.mask	boolean	<optional>		Specifies whether data should be masked or not
options.newWebSocket	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 when automaticOpen = true, or when it is called the second time.

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.

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.

Footnotes

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