The WebSocket API is an advanced technology that makes it possible to open a two-way interactive communication session between the user’s browser and a server. With this API, you can send messages to a server and receive event-driven responses without having to poll the server for a reply. – introduction from MDN

WebSocket vs HTTP

websocket vs http

The WebSocket Object

The WebSocket object provides the API for creating and managing a WebSocket connection to a server, as well as for sending and receiving data on the connection.

To construct a WebSocket, use the WebSocket() constructor.

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// Create WebSocket connection.
const socket = new WebSocket('ws://localhost:8080');

// Connection opened
socket.addEventListener('open', function (event) {
    socket.send('Hello Server!');
});

// Listen for messages
socket.addEventListener('message', function (event) {
    console.log('Message from server ', event.data);
});

WebSocket Events

  • open
  • message
  • error
  • close