WranggleRpc transport for WebSocket clients and servers

Usage no npm install needed!

<script type="module">
  import wranggleRpcWebsocketTransport from 'https://cdn.skypack.dev/@wranggle/rpc-websocket-transport';



A WranggleRpc transport, sending and receiving messages over WebSockets.


If you are using the full @wranggle/rpc package, the WebSocketTransport is already bundled within. You can import/require it with:

import { WranggleRpc, WebSocketTransport } from '@wranggle/rpc';
// or
const { WranggleRpc, WebSocketTransport } = require('@wranggle/rpc');

Unbundled Alternative

If you prefer using just the packages you need, the unbundled es6 is also available on NPM:

yarn add @wranggle/rpc-core @wranggle/rpc-websocket-transport
# or
npm install @wranggle/rpc-core @wranggle/rpc-websocket-transport 

Unbundled import:

import WranggleRpc from '@wranggle/rpc-core';
import WebSocketTransport from '@wranggle/rpc-websocket-transport';


When creating your WranggleRpc endpoint, you can use the websocket shortcut to also construct this transport, eg new WranggleRpc({ websocket: myWebsocketOpts }). See endpoint-specific instructions below.

Client-side endpoint

On the client-side (browser page or non-server process) you need to provide either a URL to the server or an existing socket.


const transport = new WebSocketTransport({
  websocketUrl: 'ws://myWebsocketServer.example'
const rpc = new WranggleRpc({ transport });

Client-side option: websocketUrl

This option creates a new WebSocket connection using the ReconnectingWebSocket library.

UPDATE deprecated reconnecting-ws lib. Have something better but need to drop it in here. (Contact/ask if needed.)

You can provide the URL as a string, a Promise resolving to one, or a function that returns one.

If you want to set options on ReconnectingWebSocket or create a socket some other way, use the clientSocket option.

Client-side option: clientSocket

This option lets you supply a socket rather have the transport create one for you. You can provide a browser-standard socket, your own ReconnectingWebSocket instance, or something else that is API compatible to either. The option accepts a socket, a Promise of one, or a function returning one.

Client-side static method: buildReconnectingWebSocket

You can create your own ReconnectingWebSocket instance with this static factory. WebSocketTransport.buildReconnectingWebSocket(...args: any[]) => ReconnectingWebSocket. It passes its arguments to the ReconnectingWebSocket constructor. Eg:

const transport = new WebSocketTransport({ 
  clientSocket: WebSocketTransport.buildReconnectingWebSocket(someUrl, [], { maxRetries: 6 }) 

Server-side endpoint

As connections are made, your WebSocket server will likely offer access to the socket object in a listener. You'll need that to set up your server-side WranggleRpc endpoint. For example:

wss.on('connection', (socket, request) => {
  if (isValidUser(request)) {
    const transport = new WebSocketTransport({ serverSocket: socket });
    const rpc = new WranggleRpc({ transport });

The wss in the above example is for a library like ws but other WebSocket servers should offer something similar.

The serverSocket attrib is required.

Additional methods

When it comes to WebSockets, you'll often want to hook into its events. Should you need to, this transport provides access to the event handlers and to the underlying socket.

  • addEventListener and removeEventListener. Forwards to the underlying socket. Params: (eventType: 'open' | 'close' | 'message' | 'error', listener: EventListener)

  • getPromisedWebSocket() => Promise<WebSocket> returns the underlying socket (once resolved should you have deferred its construction)