CS 33600 Exam 2 Review

The exam is on Monday, May 5, at 12:30 pm.

The exam is over the course material that
we covered since the first exam. The reading
assignments and code examples for the exam are
listed on the course web site.



Here are a few review problems.


Problem 1.) Identify all the parts of the following URLs.

http://www.bigcompany.com:42/consumer/products/lookup.php?sku=0&color=greenish

http://www.bigcompany.edu:4242/where/was/that/file.scm?x=2+2&bob=a4s56d7v83n

https://people.scs.carleton.ca/~lanthier/teaching/COMP1406/Notes/COMP1406_Ch12_NetworkProgramming.pdf#page=6



Problem 2.) What would be the HTTP request message (request line
and the most important request headers) for the following URL?

http://cs.pnw.edu:80/~rlkraft/cs33600/class.html#2024-03-18



Problem 3.)
How does an HTTP server know when it has received the last request header?

How does an HTTP client know when it has received the last response header?

How does an HTTP server or client know when it has received all of the entity body?

An entity body is an array of bytes. An array of bytes can be any kind of data.
How does an HTTP server or client know what the bytes in an entity body mean?



Problem 4.) Explain why, when a browser is told to GET a single URL, like

   https://www.pnw.edu/

that single URL can easily lead to many actual HTTP GET requests.



Problem 5.) Explain why, when a browser is told to GET this URL,

   http://pnw.edu/

that URL will lead to more HTTP GET requests than this URL,

   https://www.pnw.edu/



Problem 6.) If a browser sends the following HTTP request to a server,
then what was the (complete) URL in the browser's address bar?

GET /~rlkraft/cs33600/dynamic.html?data1=cats&data2=dogs HTTP/1.1
Host: math.pnw.edu
Accept: text/html,application/xhtml+xml,application/xml
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cache-Control: no-cache
Connection: keep-alive



Problem 7.) When a browser needs to send data to a dynamic web application
running on an HTTP server, the browser can use either the http GET method
or the http POST method. Give two differences between using GET and POST.



Problem 8.) What is the meaning of this HTTP response and headers?

HTTP/1.0 301 Moved Permanently
Location: http://www.MergedCompany.com/
Server: BigIP
Connection: Keep-Alive
Content-Length: 0



Problem 9.) The next few problems use the Windows curl program.

    https://curl.se/windows/microsoft.html

Explain the difference in the results of this curl command

  > curl -v -H "Accept-Encoding: gzip"  https://www.pnw.edu

and this curl command.

  > curl -v  https://www.pnw.edu



Problem 10.) Look carefully at the result from this curl command,

  > curl  https://www.google.com/search?q=Rome

and this curl command.

  > curl -A bob  https://www.google.com/search?q=Rome

What do you think explains the difference?

Hint: You can add the -v option to the curl command-lines to get more clues.



Problem 11.) Explain the difference in the results of these three curl commands.

  > curl  http://cs.pnw.edu/~rlkraft/cs33600/cs33600.html

  > curl -H "If-Modified-Since: Mon, 21 Apr 2025 00:00:00 GMT"  http://cs.pnw.edu/~rlkraft/cs33600/cs33600.html

  > curl -H "If-Modified-Since: Mon, 6 Jan 2025 00:00:00 GMT"  http://cs.pnw.edu/~rlkraft/cs33600/cs33600.html

Hint: Add the -v option to the curl command-lines to get more clues.



Problem 12.) Explain the difference in the results of this curl command

  > curl  http://cs.pnw.edu/~rlkraft/cs33600/cs33600.html

and this curl command.

  > curl -H "Range: bytes=1000-1400"  http://cs.pnw.edu/~rlkraft/cs33600/cs33600.html

Hint: Add the -v option to the curl command-lines to get more clues.



Problem 13.) Why doesn't the HTTP protocol use a sentinel value to mark
the end of an entity body?



Problem 14.) Run the http server from class.
   http://cs.pnw.edu/~rlkraft/cs33600/for-class/http_server.zip

Enter this URL into your browser.

   http://localhost:8080/static.html#part2

What URL is sent by the browser to the server? Why?
What is displayed by the browser? Why?

Use curl with the same URL.

> curl -v  http://localhost:8080/static.html#part2

What URL did curl send to the server? What was sent back
by the server to the curl client? What happened to the
fragment?



Problem 15.) How are the HTTP "Connection: close" and
"Connection: keep-alive" headers used? Be sure to explain
their use as both a request header and a response header.



Problem 16.) (a) If a browser makes an HTTP GET request for
the following HTML file, how many other HTTP requests will the
browser make? Explain why.

<!doctype html>
<html lang="en">
  <head>
    <link rel="stylesheet" href="styles/home.css">
    <script src="src/home.js"></script>
  </head>
  <body>
    <p><img src="images/logo.png"></p>
    <p>Go to <a href="page2.html">Page 2</a></p>
    <p>Go to <a href="page3.html">Page 3</a></p>
    <p>Go to <a href="page4.html">Page 4</a></p>
    <p><img src="images/footer.png"></p>
  </body>
</html>


(b) If the original GET request was to this URL
       http://www.example.com/page1.html
then show exactly what the HTTP request message will look like
for each one of the additional GET requests.



Problem 17.) If a browser makes an HTTP GET request for
the following HTML file, how many other HTTP requests will
the browser make? Explain why.

<!doctype html>
<html lang="en">
  <head>
  <meta charset="utf-8">
  <title>Home page</title>
  </head>
  <body>
    <article id="part1">
      <h3>Try our <a href="https://en.wikipedia.org/wiki/HTML_form">HTML form</a>.</h3>
      <form method="get" action="createWebPage.php">
        <input type="text" name="textData">
        <input type="reset">
        <input type="submit"><br>
        <label for="dateData">Date:</label>
        <input type="date" name="dateData"><br>
      </form>
    </article>
  </body>
</html>



Problem 18.) For the following HTML form, give an example
of what the HTTP GET request line might look like when
the user clicks on the submit button.

Hint: Experiment with the html pages from the "public_html" sup-folder of
http://cs.pnw.edu/~rlkraft/cs33600/for-class/http_server_ex.zip


  <form method="get" action="dynamicGet.html"
    <input type="reset">
    <input type="submit"><br>
    <label for="rangeData">Range:</label>
    <input type="range" name="rangeData"><br>
    <label for="numberData">Number:</label>
    <input type="number" name="numberData" value="0"><br>
    <label for="checkbox">Check:</label>
    <input type="checkbox" name="checkbox" id="checkbox3">
    <label for="selectData">Fruit:</label>
    <select name="selectData">
      <option>apples</option>
      <option>pears</option>
      <option>grapes</option>
    </select><br>
    <label for="radioButton">Radio:</label>
    <input type="radio" value="1" name="radioButton">
    <input type="radio" value="2" name="radioButton">
    <input type="radio" value="3" name="radioButton">
  </form>



19.) The following four URLs all work and will get you to
the Google search page. But these URLs are not equivalent
to each other. How are they related? Give your answer in
terms of the HTTP protocol. That is, what happens when
you do an HTTP GET on each of these URLs?

   http://google.com
   http://www.google.com
   https://google.com
   https://www.google.com

Which URL is really the Google search URL? Why?

Hint: Load each URL into Chrome with Chrome's Dev-Tools
open to its "Network" tab. Or, download each URL using
Curl with appropriate command-line options.



20.) (a) What happens if the server says Content-Length is 200
but the server only sends 100 bytes?

(b) What happens if the server says Conten-Length is 100
but the server sends 200 bytes?

(c) How do the answers to (a) and (b) depend on a persistent connection?

Hint: You can modify the source coode to the server HttpServer_v2.java in
http://cs.pnw.edu/~rlkraft/cs33600/for-class/http_server.zip
so that the server lies about the content length. Then see how
the Chrome browser or the Curl client react.