1
h13
CS56 M16
Name:
(as it would appear on official course roster)
Umail address: @umail.ucsb.edu section
9am or 10:30am
Optional: name you wish to be called
if different from name above.
Optional: name of "homework buddy"
(leaving this blank signifies "I worked alone"

h13: Threads and Sockets (Networking) (HFJ 15)

ready? assigned due points
true Tue 07/19 09:30AM Thu 07/21 09:30AM

You may collaborate on this homework with AT MOST one person, an optional "homework buddy".

MAY ONLY BE TURNED IN IN THE LECTURE/LAB LISTED ABOVE AS THE DUE DATE,
OR IF APPLICABLE, SUBMITTED ON GRADESCOPE. There is NO MAKEUP for missed assignments;
in place of that, we drop the three lowest scores (if you have zeros, those are the three lowest scores.)

Please read HFJ Chapter 15, then answer these questions.

  1. (10 pts) Please fill in the information at the top of this homework sheet, including your name and umail address. Put the time your discussion section starts (either 9am or 10:30am) in the space indicated. If the other two items apply, please fill them in as well. Please do this every single time you submit homework for this class.
  2. What does it mean for a thread to be:
    1. (4 pts) new
    2. (4 pts) runnable
    3. (4 pts) running
    4. (4 pts) blocked

  3. (3 pts) When you create a new thread which of these four states above does it go into? (circle one):

    new runnable running blocked
           

  4. (3 pts) When you call the .start() method of a thread, which of the four states above does it go into? (circle one):

    new runnable running blocked
           
  5. (4 pts) What puts a thread into the new state?
  6. (4 pts) What puts a thread into the runnable state?
  7. (4 pts) What puts a thread into the running state?
  8. Give two examples of events that can move a thread into a blocked state.
    1. (3 pts)
    2. (3 pts)

  9. (10 pts) You are creating a socket by calling new Socket("127.0.0.1",20000) and you get a BindException. What does this mean, and what should you do to try to fix this? (Hint: see the reading notes online at HFJ Chapter 15–linked to from the online version of this Homework assignment.)

  10. Briefly describe the role of each of these in setting up communication over the network between two running Java programs
    1. (5 pts) an IP address
    2. (5 pts) a port number
    3. Suppose you need to choose a port number to listen for connections on.
      1. (5 pts) What is the range of numbers that you should always avoid?
      2. (5 pts) What is the highest number that a port number can possibly be?

    4. (20 pts) Read in Chapter 15 about how you read data from a Socket and write data to a Socket. Then, in the space below, write a class rawPrintFromCSWebserver with a main method that will:

      • connect to IP address 128.111.27.14 (www.cs.ucsb.edu) on port 80 (the web server port)
      • send the following string over the connection: "GET / \n" (don’t include the quote marks)
      • read 20 lines of text, and print each of them out on System.out
      • close the connection

      Suggestion: try to write this by hand first, then type it in on the system and test it out. You should get the first 20 lines that show up if you did a “view source” on the CS dept. home page. Note: if that IP address doesn’t work, type this at the Unix prompt and see what IP address comes up: telnet www.cs.ucsb.edu 80
      Use ^] (Ctrl-close-bracket) to get back to a telnet> prompt, and type quit to quit.