Have you encountered WebSocket?

WebSocket is a protocol for establishing a persistent, two-way communication channel between a client and a server over TCP. Unlike traditional HTTP, where the client makes a request and receives a response, WebSocket allows the server to send data to the client at any time without an additional request.

It is used for implementing chats, online games, notification systems, and other applications where low latency and a constant connection are important.

Example of usage in JavaScript:

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