What is the WebSocket protocol and what is its essence, when is it used?

WebSocket is a communication protocol that provides a full-duplex channel between the client and server over a single TCP connection. Unlike traditional HTTP, where the client initiates requests, WebSocket allows the server to send data to the client at any time without a new request.

WebSocket is used where fast and persistent communication is needed, for example:

• Online chats
• Real-time games
• Financial trading platforms
• Notification systems

Example of creating a WebSocket on the client side in JavaScript:

const socket = new WebSocket('wss://example.com/socket');
socket.onopen = () => {
  socket.send('Hello server!');
};
socket.onmessage = event => {
  console.log('Message from server:', event.data);
};