The WebSocket API

Microsoft Edge supports the WebSocket API as defined in the World Wide Web Consortium (W3C)'s WebSocket API spec. WebSockets technology provides a new W3C JavaScript API and protocol for two-way communication over the internet. This new protocol makes it easier to work directly with fixed data formats, and it bypasses the slower document-based HTTP protocol.

The current HTTP standard protocol is slow because it must request documents from a server and wait for the document to be sent before it can display a webpage. With WebSockets, you can send and receive your data immediately using text, binary arrays, or blobs.

The WebSocket API is simple, requiring very little code. You can easily take advantage of low-latency, bidirectional data interchanges that will help you create faster online games, instant social network notifications, real-time displays of stock and weather information, and other timely data.

Implementing WebSockets

Implementing this new data interchange technology is simple:

  1. Use a client browser that implements the WebSocket protocol.
  2. Write code in a webpage that creates a client WebSocket.
  3. Write code on a web server that responds to a client request through a WebSocket.

Using a WebSocket client

The WebSocket protocol uses the following URI schemes:


Writing WebSocket client code

Your webpage code must do the following:

  1. Initialize the websocket and connect to the server.
  2. Test to see whether it was successful.
  3. Send and receive data.

To define the websocket URL, the below code works:

var host = 'ws://';

The following snippet shows how to connect to a WebSocket and then test to see whether it was successful:

var host = "ws://sample-host/echo";
try {
    socket = new WebSocket(host);

    socket.onopen = function (openEvent) {
       document.getElementById("serverStatus").innerHTML = 
          'WebSocket Status:: Socket Open';

    socket.onmessage = function (messageEvent) {
        if ( instanceof Blob) {
            var destinationCanvas = document.getElementById('destination');
            var destinationContext = destinationCanvas.getContext('2d');
            var image = new Image();
            image.onload = function () {
                destinationContext.clearRect(0, 0, 
                destinationCanvas.width, destinationCanvas.height);
                destinationContext.drawImage(image, 0, 0);
            image.src = URL.createObjectURL(;
        } else {
            document.getElementById("serverResponse").innerHTML = 
              'Server Reply:: ' +;

    socket.onerror = function (errorEvent) {
        document.getElementById("serverStatus").innerHTML = 
          'WebSocket Status:: Error was reported';

    socket.onclose = function (closeEvent) {
        document.getElementById("serverStatus").innerHTML = 
          'WebSocket Status:: Socket Closed';
catch (exception) { if (window.console) console.log(exception); }

function sendTextMessage() {
    if (socket.readyState != WebSocket.OPEN) return;

    var e = document.getElementById("textmessage");

function sendBinaryMessage() {
    if (socket.readyState != WebSocket.OPEN) return;
    var sourceCanvas = document.getElementById('source');

The previous code assumes you have serverStatus, destination, serverResponse, textmessage, and serverData as elements with IDs in your webpage. The result of the catch will be displayed in the console window if F12 developer tools is running.

To send text message data, use the following code:

var e = document.getElementById("msgText");

The previous code example assumes that you have the message text you want to send in a msgText element that includes the ID in your webpage. Similarly, you can use the onmessage event to detect new messages or send a message to the server by using the send method. The send method can be used to send text, binary arrays, or blob data.

Write WebSocket server code

Server code that handles sockets can be written in any server language. Whatever language you choose, you must write code that accepts WebSocket requests and processes them appropriately.

WebSocket programming

Here are the objects, methods, and properties related to WebSockets.

Name Type Description
WebSocket object Provides bidirectional channel to remote host.
close method Closes a websocket.
send method Sends data to a server using a websocket.
binaryType property Binary data format received by onmessage.
bufferedAmount property Number of data bytes queued using send.
extensions property Reports the extensions that the server selected.
onclose property Event handler called when the socket is closed.
onerror property Event handler called when there is an error.
onmessage property Event handler to notify that a message is received.
onopen property Event handler called if the websocket connected.
protocol property Reports the protocol the server selected.
readyState property Reports the state of the websocket connection.
url property Reports the current URL of the socket.

API reference

WebSocket API


The WebSocket API