What is WebSocket?

Normally, web communication works via HTTP. A client sends a request, the server responds, and the connection ends.
But what if you need real-time updates — like in chat apps, online games, or stock tickers?
Opening a new HTTP request for every update would be too slow and heavy.

That’s where WebSocket comes in.

Key Idea

• WebSocket creates a persistent, two-way connection between client and server.
• Instead of “ask and reply”, both sides can send messages anytime.
• It starts as an HTTP request, then “upgrades” the connection to WebSocket.

Why WebSocket?

• Real-time communication (chats, notifications, multiplayer games).
• Efficiency — no need to reopen connections all the time.
• Bi-directional — both client and server can send data.

Example in JavaScript

// Client-side WebSocket
const socket = new WebSocket("ws://localhost:8080");

// When connection opens
socket.onopen = () => {
  console.log("Connected to server");
  socket.send("Hello Server!");
};

// When message is received
socket.onmessage = (event) => {
  console.log("Message from server:", event.data);
};

On the server side (Node.js example with ws):

const WebSocket = require("ws");
const server = new WebSocket.Server({ port: 8080 });

server.on("connection", (socket) => {
  console.log("Client connected");
  socket.on("message", (msg) => {
    console.log("Received:", msg);
    socket.send("Echo: " + msg);
  });
});

Summary

• WebSocket = always-open, two-way connection between client and server.
• Perfect for real-time apps.
• Starts as HTTP, upgrades to WebSocket.
• Simpler and faster than polling for frequent updates.