Assignment #2: Socket Programming Project


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Assignment #2: Socket Programming ProjectCMPT 371 Assignment #2

PART I: Socket Programming Project (to be submitted as a zip file on Coursys)
In this programming project, you will develop a simple calculator application using socket programming in Python. You will build this project in two steps starting with provided skeleton
code for a chat application. You will have to modify the skeleton code to fulfill the requirements.
Step 1: The skeleton server code named and client code named
are stored as a zip file which can be accessed using a link on the Homework page of the course
website. The server is a TCP server which waits for a connection request from a TCP client.
The client should be able to send a connection request to the server. After the connection is
accepted by the server, the server and client enter into the chat mode. Most of the code for
chatting is already provided. The first step of the assignment is to fill in the missing code where
you find . . . in the skeleton code so that server and client can talk to each other.
The code provided runs with Python 3 and was tested (before some lines were replaced with
. . .) in a Linux environment. It should run on Windows and Mac as well (but it was not tested
on Windows or Mac). Be sure that you have Python 3 or later installed on your computer.
It will not run correctly with Python 2.7 or earlier. Running the programs is easy. After you
complete the two files, open two terminals (one for the server and one for the client) and change
directory to where you have stored the files. Run from one terminal and then from the other terminal (the server must run before the client). You should be
able to run the programs using the following commands (one in each terminal).
python3 (to start server)
python3 (to start client)
Your code should work locally (without an external IP). You should use localhost as your
IP address in the code. (You can change it to something else later if you are interested.) If
everything works, the client and server should be able to alternate sending messages to each
other as shown in Figure 1. Typing q and Enter in either terminal will close the connection.
(This part is already done in the skeleton code.)
Figure 1: Simple chat application screen capture
In summary, Step 1 is to complete the server and client so that the chat application works as
expected. Save the files as and (you will submit these files).
Step 2: After completing Step 1, you should have a simple but functional chat application. In
Step 2, you will modify the code to implement a calculator client-server application.
The server receives requests from clients to perform arithmetic calculations and returns the
calculated values to the clients. The server should be initiated once before any clients are
started and should be able to serve multiple requests from the same or different clients. The
server can use the “eval” operation of python to evaluate the input received from the clients.
The documentation for the eval operation in Python is here:
The clients connect to the server with requests for equations to be evaluated and then print the
results. A client should be able to terminate its connection with the server in a clean manner
(by sending q).
Client1 sends: 2*3*4*5
Server runs eval(2*3*4*5) and returns the result 120 to Client1
Client1 prints 120
Client2 sends: 2+3+4+5
Server runs eval(2+3+4+5) and returns the result 14 to Client2
Client2 prints 14
Client2 sends: q
Client1 sends: (1+3)*(5-2)
Server runs eval((1+3)*(5-2)) and returns the result 12 to Client1
Client1 prints 12
Client1 sends: q
In summary, Step 2 is to complete the server and client so that the calculator application works
as expected. Save the files as and (you will submit these files).
IMPORTANT: Start from the skeleton code provided and do not change the function names and program structures. Only modify the code where necessary. We
will test your code with a script and it must pass our tests for you to receive credit.
Both server and client should run on localhost. So even if you experiment with
other IP addresses, before submission please make sure they work on localhost
without any external network connection. We will use Python 3 or later to run the
test scripts.
Submission: Submit four python files and a few screen captures of your working chat and
calculator applications (as a single zip file) to Coursys. Python files to be submitted are:
PART II: Questions on Chapters 2 and 3 (to be submitted in the course assignment box)
1. A file of F = 10 Gbits needs to be distributed to N clients/peers. The source node which
contains the file has an upload rate of us = 40 Mbps, and each client/peer has a download rate
of di = 3 Mbps and upload rate u. For N = 10, 20, 40 and u = 256 Kbps, 512 Kbps, 1 Mbps,
prepare tables showing the minimum distribution time for both client-server distribution and
peer-to-peer distribution for each combination of N and u. Note: Use 1 Gbps = 1024 Mbps
and 1 Mbps = 1024 Kbps for this question.
2. UDP and TCP use a 1s complement checksum to detect bit errors (flipped bits).
(a) Compute the 1s complement checksum of the following three 16-bit words showing all
of your work: 1101001101000100, 0111100001010101, 1110101110000101.
(b) Show that the checksum in part (a) can fail to detect two flipped bits.
(c) Describe the conditions that will result in the failure of the checksum of n 16-bit words
to detect two flipped bits.
Note: part (b) is asking for a specific example; part (c) is asking for general conditions.
PART III: Wireshark Lab 2 (to be submitted in the course assignment box)
The link to Wireshark Lab 2 is on the Homework page of the course website. You should do the
lab with a live connection, not the traces mentioned in the second footnote.

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