ws module

Learn WebSocket servers with the ws module.

What is the ws module?

ws is the most popular lightweight WebSocket module for Node.js. WebSocket provides a bidirectional, persistent connection between server and client; unlike HTTP it does not reconnect per request.

Install: npm install ws. WebSocket is ideal for real-time apps: chat, live notifications, games. The ws module is low-level; for higher-level features use Socket.io. But ws is lighter and has less overhead. You import it with require("ws").

WebSocket vs HTTP

HTTP is request-response based: the client asks, the server answers, the connection closes. WebSocket keeps the connection open; either side can send a message at any time.

This is critical for real-time apps. In a chat app the server can push a new message instantly; it does not wait for the client to ask. WebSocket starts with an HTTP handshake, then upgrades to the WebSocket protocol. That is why it uses the same ports (80/443).

Exercise Log the type of WebSocketServer

Import the WebSocketServer class from ws. Log typeof WebSocketServer.

Show example solution

const { WebSocketServer } = require("ws");
console.log(typeof WebSocketServer);

Test yourself

What does the ws module provide?
- A persistent two-way connection
- One-way HTTP
- File compression
- Network acceleration
Show answer

A persistent two-way connection — The ws module provides a bidirectional persistent connection.

Complete the module name

const { WebSocketServer } = require("____")

Show answer

const { WebSocketServer } = require("ws")

Match each piece to its role

ws

WebSocket module
WebSocketServer

Server class
npm install ws

Installs the module
require("ws")

Imports the module

Next lesson: WebSocket server

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