Retransmitting-WebSocket

A tiny zero dependency wrapper around a WebSocket to ensure no messages are lost after a network failure. This is useful if you are dealing with a stateful/mutable protocol over network. Retransmitting-WebSocket ensures messages do not get lost nor are they sent or received multiple times. Retransmit also handles reconnecting for you.

This project was created for use in Greenfield

Usage

Both sides need to wrap their WebSocket in a RetransmittingWebSocket. This RetransmittingWebSocket is stateful so make sure that the same 2 are talking to each other on reconnect.

import ReconnectingWebSocket from 'reconnecting-websocket'
import { RetransmittingWebSocket } from 'retransmit.js'

// all options are optional
const retransmittingWebSocket = new RetransmittingWebSocket({
  maxUnacknowledgedBufferSizeBytes: 100000, // Maximum cummulative size of all received messages before we confirm reception.
  maxUnacknowledgedMessages: 100, // Maximum cardinal size of all received messages before we confirm reception.
  maxUnacknowledgedTimeMs: 10000, // Time after last messages before we confirm reception.
  closeTimeoutMs: 1500000, // Maximum time after network failure before we consider the connection closed.
  reconnectIntervalMs: 3000, // Reconnection interval. Time to wait in milliseconds before trying to reconnect.
  webSocketFactory: () => { new WebSocket(myURL) } // Function to use for creating a new web socket when reconnecting.
})

// No need to make ReconnectingWebSocket queue messages, RetransmittingWebSocket will take care of it.
retransmittingWebSocket.useWebSocket(new WebSocket('ws://my.site.com')) // .
//☝️ The used WebSocket can be swapped on the fly. This is required server-side so you can use a new incoming 
// WebSocket instance each time the old one is disconnected. The only requirement is that the other side keeps using the same 
// retransmittingWebSocket object.

retransmittingWebSocket.onmessage = (event) => {
  // Simply handle application payload here like you would with a normal WebSocket.
}


const somePayload = new Uint8Array([1,2,3,4])
retransmitter.send(somePayload) // retransmitter ensures the payload will be delivered exactly once, regardless of the connection state.