web-socket.md

Class: WebSocket extends EventTarget

Create WebSocket connections from the main process using Chromium's native networking library

Process: Main

net.WebSocket is a drop-in replacement for the WHATWG WebSocket interface that routes the connection through Chromium's network stack rather than Node.js. Use it when you want a main-process WebSocket connection that:

• Uses the system or session proxy configuration (PAC, WPAD).
• Validates TLS certificates against the platform trust store and the session's certificate verification policy.
• Honors session-level configuration (custom CA, host resolution rules, etc.).
• Sends the session's cookies (when useSessionCookies is enabled).

The class implements the standard WebSocket interface (an EventTarget), so code written against the browser or Node.js global WebSocket works without changes:

const { app, net } = require('electron')

app.whenReady().then(() => {
  const ws = new net.WebSocket('wss://echo.websocket.events')
  ws.onopen = () => ws.send('hello')
  ws.onmessage = (event) => {
    console.log('received', event.data)
    ws.close()
  }
})

net.WebSocket can only be used after the application emits the ready event.

new WebSocket(url[, protocols])

• url string - The URL to connect to. The scheme must be ws: or wss: (http: and https: are accepted and rewritten to their WebSocket equivalents, as in the browser).
• protocols string | string[] | WebSocketOptions (optional) - One or more WebSocket subprotocols, or an Electron-specific options object.

Passing an options object as the second argument is an Electron extension; the two-argument form new net.WebSocket(url, protocols) is fully compatible with the WHATWG constructor.

Static Properties

WebSocket.CONNECTING Readonly

An Integer constant equal to 0, the readyState value while the opening handshake is in progress.

WebSocket.OPEN Readonly

An Integer constant equal to 1, the readyState value once the connection is established.

WebSocket.CLOSING Readonly

An Integer constant equal to 2, the readyState value while the closing handshake is in progress.

WebSocket.CLOSED Readonly

An Integer constant equal to 3, the readyState value once the connection is closed.

Instance Properties

ws.url Readonly

A string representing the resolved URL of the connection.

ws.readyState Readonly

An Integer representing the current state of the connection: one of WebSocket.CONNECTING (0), WebSocket.OPEN (1), WebSocket.CLOSING (2), or WebSocket.CLOSED (3).

ws.bufferedAmount Readonly

An Integer representing the number of bytes of application data that have been queued via send() but not yet handed off to the network.

ws.protocol Readonly

A string containing the subprotocol selected by the server. The empty string until the connection is open or if the server did not select a subprotocol.

ws.extensions Readonly

A string containing the extensions negotiated by the server (for example permessage-deflate).

ws.binaryType

A string controlling how incoming binary messages are exposed on the message event. Can be nodebuffer, arraybuffer, or blob. The default is nodebuffer.

'nodebuffer' is an Electron extension that delivers binary messages as Buffer objects, which is generally the most convenient representation in the main process. Set binaryType to 'arraybuffer' or 'blob' for behavior identical to the renderer WebSocket.

ws.onopen

A Function | null event handler for the open event. Equivalent to calling addEventListener('open', ...).

ws.onmessage

A Function | null event handler for the message event. Equivalent to calling addEventListener('message', ...).

ws.onerror

A Function | null event handler for the error event. Equivalent to calling addEventListener('error', ...).

ws.onclose

A Function | null event handler for the close event. Equivalent to calling addEventListener('close', ...).

Instance Methods

ws.send(data)

• data string | ArrayBufferLike | ArrayBufferView | Blob - The data to send. Strings are sent as text frames; everything else is sent as a binary frame.

Enqueues data to be transmitted to the server. Throws an InvalidStateError DOMException if readyState is CONNECTING.

ws.close([code][, reason])

• code Integer (optional) - The WebSocket close code. Must be 1000 or in the range 3000–4999.
• reason string (optional) - A human-readable close reason. Must encode to no more than 123 bytes of UTF-8.

Closes the connection. Calling close() while still CONNECTING aborts the handshake.

Events

net.WebSocket is an EventTarget, not an EventEmitter. Listen with addEventListener() or the corresponding on* event handler property:

• open - Emitted when the connection is established and the opening handshake has completed. After this event, protocol and extensions reflect the values negotiated with the server.
• message - Emitted with a MessageEvent when a message arrives. event.data is a string for text frames, or a Buffer, ArrayBuffer, or Blob (per binaryType) for binary frames.
• error - Emitted when the connection fails. Always followed by a close event.
• close - Emitted with a CloseEvent (code, reason, wasClean) when the connection is closed for any reason. When the connection fails (for example, the handshake is rejected or the network is unreachable), code is 1006 and Electron sets reason to a short description of the underlying network error so that the failure is diagnosable without a debugger attached.