ws library for WebSocket server in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the ws library in Node.js?

The ws library is used to create WebSocket servers and clients in Node.js, enabling real-time, two-way communication between a server and browser or other clients.

beginner

How do you create a basic WebSocket server using the ws library?

You create a WebSocket server by importing <code>WebSocketServer</code> from <code>ws</code> and then instantiating it with a port number, like:<br><pre>const { WebSocketServer } = require('ws');
const wss = new WebSocketServer({ port: 8080 });</pre>

beginner

What event do you listen to for new client connections on a ws WebSocket server?

You listen to the 'connection' event on the WebSocket server instance to handle new client connections.

beginner

How can you send a message to a connected client using the ws library?

You use the send() method on the client WebSocket object inside the 'connection' event handler, like ws.send('Hello client!').

beginner

Why is it important to handle the 'message' event on a WebSocket client connection?

Handling the 'message' event lets the server receive and process data sent from the client, enabling interactive real-time communication.

Which method creates a WebSocket server with the ws library?

A ws.createServer(8080)

B new WebSocketServer({ port: 8080 })

C new WebSocketClient({ port: 8080 })

D ws.startServer(8080)

The WebSocketServer class is used to create a WebSocket server instance.

What event should you listen to for new client connections?

A 'connection'

B 'client'

C 'open'

D 'connect'

The 'connection' event fires when a new client connects to the server.

How do you send a message to a client in ws?

A client.send(message)

B client.emit('send', message)

C server.send(client, message)

D ws.sendToClient(message)

The send() method on the client WebSocket object sends data to that client.

Which of these is NOT a valid use of the ws library?

A Creating a WebSocket server

B Creating a WebSocket client

C Handling HTTP requests

D Sending real-time messages

The ws library handles WebSocket connections, not HTTP requests.

What event do you listen to for receiving messages from a client?

A 'input'

B 'data'

C 'receive'

D 'message'

The 'message' event is triggered when the server receives data from a client.

Explain how to set up a simple WebSocket server using the ws library in Node.js.

Think about the steps from starting the server to talking with clients.

Describe the role of the 'connection' and 'message' events in a ws WebSocket server.

Focus on how the server interacts with clients.