Training Guide: Programming in HTML5 with JavaScript and CSS3 Ebook

436 CHAPTER 10 WebSocket communications

Answers

This section contains the answers to the lesson review questions in this chapter.

Lesson 1

1. Correct answer: C
   A. Incorrect: The onopen event is triggered when the connection is opened.
   B. Incorrect: The onclose event is triggered when the connection is closed.
   C. Correct: The onmessage event is triggered when data is received.
   D. Incorrect: The onerror event is triggered when an error is thrown.


2. Correct answer: B
   A. Incorrect: SignalR does not work with Node.js websites.
   B. Correct: The Socket.IO library works with Node.js to provide a browser-
   independent library for WebSocket communications.
   C. Incorrect: FarmSockets does not exist.
   D. Incorrect: AgnosticSocket does not exist.


3. Correct answer: B
   A. Incorrect: If you wait until the connection is closed, you will need to create a new
   WebSocket object.
   B. Correct: You can add code to send empty messages periodically.
   C. Incorrect: There is no keepAlive property on the WebSocket object.
   D. Incorrect: If you create a new WebSocket object each time you send a message,
   the server will think that new browsers are communicating with it.