Project #1: Warmup: Socket programming 101

Project #1: Warmup: Socket programming 101
CS 352 Internet Technology

The goal of this project is to help you explore Python programming and specifically Python’s
socket programming interface. Further, this exercise will serve as a foundation for at least one
upcoming programming project on asynchronous sockets.
Starting with the sample working code in proj.py, you will construct two programs client.py
and server.py which communicate with each other over the socket API. Currently, proj.py
consists of server code and client code written as two separate threads.
How to work through this project
Step 1: Understand the functionality as is
Understand the functionality implemented in the proj.py program. First, download, save and
execute the program as is in your ilab environment. Make sure it executes successfully and
according to how you would expect.
For example, you might see something like this if you run the command python proj.py on
your ilab machine terminal.
[S]: Server socket created
[S]: Server host name is porthos.cs.rutgers.edu
[S]: Server IP address is 128.6.25.90
[C]: Client socket created
[S]: Got a connection request from a client at (’128.6.25.90’, 59814)
[C]: Data received from server: Welcome to CS 352!
Done.
Step 2: Remove sleeps and re-run
Remove the two statements in the program that say time.sleep(5). Now run the program once,
and run it immediately again after it finishes successfully.
What do you see? Can you explain why?
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Step 3: Separate proj into two programs
Separate the server code and client code into two different programs, server.py and client.py.
Execute the server program first and then execute the client program. You should still get the same
set of print messages as in the combined threaded code in proj.py.
Step 4: Reversing the message
In the program provided, the server just sends a message string to the client after it connects.
Modify the server so that when the client sends a string to the server, the server reverses the string
before sending it back to the client. For example, if the client sends HELLO to the server, the
client should receive OLLEH. Your client program should print the string sent by the client and the
corresponding string received by the client from the server.
Step 5: Reading strings from a file
Now make your client program read each line from an input file in-proj.txt and send it to the
server. Your server program should print each reversed output to a file out-proj.txt. Your
output filename must match exactly with the one shown. A sample input file is provided. You are
welcome to modify this file and try with your own sample inputs. If it helps, you may assume each
line will be at most 200 characters long. The input file may contain multiple lines. Each input line
may contain any character that can be typed on a standard US qwerty keyboard, including space.
Some helpful notes
(1) A reference output file is provided in sample-out-proj.txt.
(2) If you run proj.py on certain machines (not ilab), for example, on your laptop directly, you
might see an error if name resolution fails. Here is an example when running proj.py on my
Apple Mac OS Mojave machine:
[S]: Server socket created
[S]: Server host name is APPLEs-MacBook-Pro.local
[C]: Client socket created
Exception in thread server:
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threadingline 810, in bootstrap inner
self.run()
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threadingline 763, in run
self. target(*self. args, **self. kwargs)
File "proj.py", line 20, in server
localhost ip = (socket.gethostbyname(host))
gaierror: [Errno 8] nodename nor servname provided, or not known
Done.
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Exception in thread client:
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threadingline 810, in bootstrap inner
self.run()
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threadingline 763, in run
self. target(*self. args, **self. kwargs)
File "proj.py", line 43, in client
localhost addr = socket.gethostbyname(socket.gethostname())
gaierror: [Errno 8] nodename nor servname provided, or not known
The program failed with the above error because the local host name could not be resolved
through the gethostbyname call.
(3) If you’re connected on a VPN when you’re running proj.py on your local machine (not ilab),
the program may not work as expected because the client may be unable to connect to the server
using the machine’s VPN IP address. Here is an example of this error on my laptop:
[S]: Server socket created
[S]: Server host name is ipo3912l132.rad.rutgers.edu
[S]: Server IP address is 10.66.6.157
[C]: Client socket created
Done.
Exception in thread client:
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threadingline 810, in bootstrap inner
self.run()
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/threadingline 763, in run
self. target(*self. args, **self. kwargs)
File "proj.py", line 47, in client
cs.connect(server binding)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.pyline 228, in meth
return getattr(self. sock,name)(*args)
error: [Errno 60] Operation timed out
(4) How we will run your code: We will run your client and server programs with the commands
python server.py and python client.py, using Python version 2 on the ilab machines.
What to submit
You must submit three files: your client.py, server.py, and report.pdf. The report must
be in PDF file format. Please compress the files into a single Zip archive before uploading to
Canvas. Only one team member must submit.
The client and server must implement all functionality up to step 5.
Your report must answer the following questions.
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1. Team details: Clearly state the names and netids of your team members (there are 2 of you).
2. Collaboration: Who did you collaborate with on this project? What resources and references did you consult? Please also specify on what aspect of the project you collaborated or
consulted.
3. What did you observe after running step 2 above? Can you explain why you see what you
see?
4. Is there any portion of your code that does not work as required in the description above?
Please explain.
5. Did you encounter any difficulties? If so, explain.
6. What did you learn from working on this project? Add any interesting observations not
otherwise covered in the questions above. Be specific and technical in your response.
Contact the course staff on Piazza if you have any questions.
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