Server-Sent Events alternative in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a WebSocket server using the 'ws' library.

Node.js

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

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

Aserver

Bhost

Cpath

Dport

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'host' instead of 'port' will not start the server on the correct port.

The 'port' option specifies the port number the WebSocket server listens on.

2fill in blank

medium

Complete the code to send a message to all connected WebSocket clients.

Node.js

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

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

AWebSocket.OPEN

BWebSocket.CONNECTING

CWebSocket.CLOSED

DWebSocket.CLOSING

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'CLOSED' or 'CLOSING' will cause errors because the connection is not open.

Only clients with the 'OPEN' readyState can receive messages.

3fill in blank

hard

Fix the error in the WebSocket client connection code.

Node.js

const ws = new WebSocket('ws://localhost:[1]');

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

A8080

B3000

C80

D443

Attempts:

3 left

💡 Hint

Common Mistakes

Using port 80 or 443 will fail if the server is not listening there.

The server listens on port 8080, so the client must connect to that port.

4fill in blank

hard

Fill both blanks to broadcast a JSON message to all clients except the sender.

Node.js

wss.on('connection', ws => {
  ws.on('message', message => {
    wss.clients.forEach(client => {
      if (client !== ws && client.readyState === [1]) {
        client.send(JSON.[2](message));
      }
    });
  });
});

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

AWebSocket.OPEN

Bparse

Cstringify

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using JSON.parse to send messages will cause errors.

Clients must be open to receive messages, and messages must be stringified JSON to send.

5fill in blank

hard

Fill all three blanks to set up a WebSocket server that logs connection and message events.

Node.js

import WebSocket from 'ws';
const server = new WebSocket.Server({ [1]: 9090 });
server.on('[2]', ws => {
  console.log('Client connected');
  ws.on('[3]', message => {
    console.log('Received:', message);
  });
});

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

Aport

Bconnection

Cmessage

Dopen

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'open' instead of 'connection' will not work for server events.

The server listens on port 9090, listens for 'connection' events, and listens for 'message' events on each client.