COMP30023: Computer Systems Project 2 solution




5/5 - (6 votes)

The aims of Project 2 are:
• To provide you with experience in writing programs that interact with each other over a network
(socket programming).
• To provide you with experience in writing multi-threaded applications and process synchronization.
Your task consists of three components:
• To implement a server capable of handling multiple concurrent requests for the game ‘Mastermind’.
See (board game) for an overview of the game.
• To implement a client program that can be used to test your game server.
• To report on server resources usage (performance metrics and other interesting statistics).
Note: a ‘simple’ game was selected for the project, so that you can devote all (most) of your effort to
the concurrency issues rather than getting ‘bogged down’ with game playing strategies.
Your programs must be written in C.
The executables programs must be called server and client respectively. Your programs must run
on both the School of Engineering Linux server and your NeCTAR
cloud VM (your executable must run on the OS configuration adopted, with an accessible port).
Rules of Mastermind (for this project)
Mastermind is a two-player game consisting of a ‘codemaker’ and a ‘codebreaker.’ The codemaker
secretly selects a code consisting of an ordered sequence of four colours c1c2c3c4, each chosen from the
set {A, B, C, D, E, F} of six possible colours, with repetitions allowed.
The codebreaker then tries to guess the code by repeatedly submitting their nominated sequence of four
colours from the set {A, B, C, D, E, F}.
After each guess, the codemaker provides feedback to the codebreaker using two numbers: the number of
correct colours in the correct positions b and the number of colours that are part of the code but not in
the correct positions m, using the format [b:m]. For example, if the code is ABCC and the codebreaker’s
guess is BCDC, then the codemaker’s response would be [1:2] since the codebreaker has guessed the
second C correctly and in the correct position, while having guessed the B and the first C correctly, but
in the wrong position.
The codebreaker continues guessing until he/she guesses the code correctly, or until he/she reaches a
maximum allowable number of guesses (set to 10 in this project) without having correctly identified the
secret code.

We are not imposing tight constraints on design/requirements – you are free to design your server and
client programs as you see fit. However, your implementation must meet the criteria described below:
Implementation overview
• Your server program will play the role of the ‘codemaker.’ Your client program will play the
role of the ‘codebreaker.’
• Your server program must be able to handle multiple/concurrent requests from individual clients
(typically running on hosts with different IP addresses to the server). See Figure 1.
– that is, your server program must be able to carry on multiple game sessions with separate clients simultaneously, rather than delaying new connections until the current session is
• You must make use of Pthreads to process each client’s interactions with the server.
• When you implement sockets, you must use TCP (SOCK STREAM for AF INET).
• Your server program uses the following command line arguments:
– a port number
– a default four character string representing the secret code (e.g., AAAA) that can be used for
testing your code — if this argument is not supplied, your server program will randomly
generate the secret code
• Your client program uses the following command line arguments:
– an IP address (or host name) of the server
– the corresponding port number
• It is important to note that clients do not play games against each other. ie. a client plays a
game against the server.
Figure 1: A simple illustration of the client-server architecture. Your server must be able to handle
concurrent requests. The server is responsible for maintaining a log file(log.txt) of interactions between
each client and the server.

Playing the game
• Your server program should send an appropriate ‘Welcome’ message to the client program,
explaining the rules of the game (the format of the message is up to you!)
• The client-server interaction general works as follows:
– the server creates the secret code
– the server requests the client to submit a guess of the secret code
– the client ‘sends’ their guess to the server
– the server checks the guess and provides feedback
– this cycle continues until either (a) the client successfully guesses the secret code, or (b)
the client uses up the maximum number of guesses allowed (10 in this case).
• Your client program should display text-based message describing the status of the game (with
appropriate messages) for each step of the game, so that the ‘human’ player has the necessary
information to make a guess of the secret code.
• To keep things simple, the only input you collect from the ‘human’ player (client) on each turn
is a string of four char values representing their guess. For example, the ‘human player’ (client)
enters ABCD representing A in column 1, B in column 2, C in column 3 and D in column 4. The
client then transfer this input string (or nominated guess) to the server for processing.
• You do not have to do error checking of user input (on the client side) – assume that the user
enters a four character string (although, they could possibly choose characters outside of the
expected range {A, B, C, D, E, F}).
• Based on the input submitted by client program, your server program should send an appropriate response:
– the feedback values [b:m] indicating the number of matching parts of the code (e.g. [1:2]
based on the example in the Rules section above), or
– an INVALID message indicating that the guess submitted was not valid (e.g., the user entered
ZZAA), or
– a SUCCESS message indicating that the secret code has been identified
Note: the client should close the connection on receipt of the SUCCESS message.
• Within a game session, the server program should keep track of how many guesses the client
program has made. If the client program has not identified the secret code after 10 attempts,
the server program sends
– a FAILURE message indicating that there are ‘no more attempts’ as well as displaying the
secret code
Note: the client should close the connection on receipt of the FAILURE message.

• You must continually write to a log file (log.txt) detailing interactions between the server and
individual clients. Each log file entry will include:
– a time-stamp (system date/time)
– IP address of the client or for the server
– a socket id (or file descriptor) for the client connection
– details of the exchange between client and server.
∗ from the server – record the secret key
∗ from the client – record the guess (e.g. BCDC) submitted
∗ from the server – record an appropriate message (e.g, [1:2] or INVALID or SUCCESS or
FAILURE with a ‘game over’ message)
See the LMS for an example log file. Note: we will not use the diff command to check your
output file against an expected output.
• Care must be taken to make sure that the concurrent processing of interactions between the server
and individual clients does not cause incorrect entries in the log file.
Investigating server resource usage / performance
In this subtask, you are asked to examine overall server ‘performance’ and resource usage and write
the results to the bottom of the log file (log.txt) when your server program shuts down – you write
to the log file after the key combination Ctr+C is used to ‘terminate’ your process.
• In the simplest case, you could report the number of clients that successfully connected to your
server (and a count of the number of clients who successfully guessed the secret code).
• You should also investigate resource usage (e.g., rusage, including timeval, and/or memory use
in Pthreads etc).
• It may also be interesting to examine the /proc (virtual file system) and other data the you can
can access via the process id.
Note: we are not being prescriptive here – your task is to identify and report on what you consider
to be ‘interesting’ statistics. If you are measuring memory usage for Pthreads, you may need to
consider using a mutex when summing/accumulating memory usage across individual threads.
Typically, the key combination Ctr+C is used to terminate processes in Linux. To shut down your
server program we will use this key combination. However, you should write an appropriate signal
handler function to ‘catch’ the Ctr+C input, which will:
• write the ‘performance’ data (statistics) to the bottom of the log file (log.txt).
• then, terminate your server program.

Report – describing resource usage / performance
Prepare a short report ( ≤ 500 words in length) named report.txt using plain text format that:
• describes the resource usage and performance data that you have collected.
• compares the values for resource usage and performance data when your sever program runs on
both and your NeCTAR cloud VM – especially examining what
happens when the number of concurrent clients increases.
You must add the file report.txt to your SVN repository.
Program execution / command line arguments
To run your sever program on (or your NeCTAR cloud VM)
prompt: ./server [port number] [default secret code]
where [port number] is a valid port number (e.g., 6543)
where [default secret code] is a valid secret code (e.g., AAAA)
To run your client program on
prompt: ./client localhost [port number]
where localhost corresponds to ‘this computer’
and [port number] is the valid port number (e.g., 6543).
To run your client program on a different host machine
prompt: ./client [host name/IP address] [port number]
where [host name/IP address] corresponds to host of your sever
and [port number] is the valid port number (e.g., 6543).
Note: A new log file log.txt file is created each time the sever program is started.

Submission details
Please include your name and login id in a comment at the top of each file.
Our plan is to directly harvest your submissions on the due date from your SVN repository.
You must submit program file(s), including a Makefile. Make sure that your makefile, header files and
source files are added/committed. Do not add/commit object files or executables. Anything you want
to mention about your submission, write a text file called README.
If you do not use your SVN repository for the project you will NOT have a submission and will be
awarded zero marks.
It should be possible to “checkout” the SVN repository, then type make server to produce the executable server and make client to produce the executable client.
Late submissions will incur a deduction of 2 mark per day (or part thereof).
If you submit late, you MUST email the lecturer, Michael Kirley <>. Failure
to do will result in our request to sysadmin for a copy of your repository to be denied.
Extension policy: If you believe you have a valid reason to require an extension you must contact
the lecturer, Michael Kirley <> at the earliest opportunity, which in most
instances should be well before the submission deadline.
• It is university policy that projects/assignment work cannot have a due date that falls during
‘Swotvac’ (the week before exams starts).
• Requests for extensions are not automatic and are considered on a case by case basis. You will be
required to supply supporting evidence such as a medical certificate.
Plagiarism policy: You are reminded that all submitted project work in this subject is to be your
own individual work. Automated similarity checking software will be used to compare submissions. It
is University policy that cheating by students in any form is not permitted, and that work submitted
for assessment purposes must be the independent work of the student concerned.
Using SVN is an important step in the verification of authorship.

Code that does not compile and run on will be awarded zero marks.
Your submission will be tested and marked with the following criteria:
• Client-Server interactions (3 marks)
– server and client programs run on
– client program displays appropriate messages (and the status of the game is displayed to
stdout) at each stage of the game
– it is possible to use the server and client programs to play a complete game correctly
• Concurrency (3 marks)
– server program is able to process a large number of concurrent games (from a variety of IP
addresses; up to 20 clients) and record interactions in the log file
Note: it it important that your client program only accepts the correct input values (a
string of four characters e.g., ABCD) representing the guess at each stage of the game – this
will allow for automated testing of your submission
• Log file (3 marks)
– correctly documents interactions between the server and multiple clients using the format
specified in the ‘Playing the game’ section.
– the ‘performance’ and resource usage data is written to the log file after the key combination
Ctr+C is used to ‘terminate’ the server program
• NeCTAR cloud deployment (2 marks)
– upload to your SVN repository a text file ip.txt that contains the IP number
for your VM and port number – without these details, we cannot test your
– server running on your VM functions correctly when tested
Note: it is your responsibility to make sure that your instance of the VM is running on the
NeCTAR cloud
• Quality of code (2 marks)
– elegant code; detailed documentation where necessary
– coding standards followed (and consistent), Makefile works, use of header files, separate source
files (where appropriate)
• Report (2 marks)
– report.txt added to your SVN repository
– the report describes additional statistics – it includes more than simply counting client
‘connects’ and games won
– comparison data included; discussion valid.