ws library for WebSocket server in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the ws library.

Node.js

const WebSocket = require('[1]');

Drag options to blanks, or click blank then click option'

Aws

Bexpress

Chttp

Dsocket.io

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' or 'http' instead of 'ws'.

Using 'socket.io' which is a different library.

The ws library is imported using require('ws'). This allows you to create a WebSocket server.

2fill in blank

medium

Complete the code to create a new WebSocket server on port 8080.

Node.js

const wss = new WebSocket.Server({ [1]: 8080 });

Drag options to blanks, or click blank then click option'

Aurl

Bhost

Caddress

Dport

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'host' or 'address' instead of 'port'.

Using 'url' which is not a valid option here.

The WebSocket.Server constructor takes an options object where 'port' specifies the port number to listen on.

3fill in blank

hard

Fix the error in the event listener to correctly handle new connections.

Node.js

wss.on('[1]', function connection(ws) {
  ws.send('Welcome!');
});

Drag options to blanks, or click blank then click option'

Amessage

Bconnection

Copen

Dconnect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'connect' or 'open' which are not valid events for the server.

Confusing 'message' event with connection event.

The 'connection' event is emitted when a new client connects to the WebSocket server.

4fill in blank

hard

Fill both blanks to send a message to all connected clients.

Node.js

wss.clients.forEach(function [1](client) {
  if (client.readyState === [2].OPEN) {
    client.send('Hello all!');
  }
});

Drag options to blanks, or click blank then click option'

AforEach

BWebSocket

Cws

Dsend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ws' instead of 'WebSocket' for the readyState constant.

Using 'send' as the function name instead of 'forEach'.

Use 'forEach' to loop over clients. The constant 'WebSocket.OPEN' checks if the connection is open.

5fill in blank

hard

Fill all three blanks to handle incoming messages and reply back.

Node.js

wss.on('connection', function(ws) {
  ws.on('[1]', function(message) {
    console.log('Received:', message.toString());
    ws.[2]('Echo: ' + [3]);
  });
});

Drag options to blanks, or click blank then click option'

Amessage

Bsend

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'close' event instead of 'message'.

Trying to send the wrong variable or forgetting to convert message to string.

The 'message' event listens for incoming messages. Use ws.send() to reply. The received message is passed as the argument.