CS341 / Assignment 4



CS341 / Assignment 4

/ Instructions
Please compress your code and README.txt file into a zip file or tar.gz.
/ Programming Assignment
Download the template Java program in Canvas: Files/
For this assignment you will create your own application layer protocol for a server that acts as a
command and control server for an ATM network.
The Server (50% of your grade)
This server will be what ATMs communicate with. As such, you need to implement the following
functionality in your protocol:
• Login – the client will pass you a user name and PIN, and your server will generate a token and
pass it back to them if successful
• Logout – the client will pass you a token, and you will log them out
• Balance – The client will pass you a token and you will pass the balance of the account
• Withdraw – The client will pass you a token and an amount to withdraw, if the amount is less
than the balance, you will pass back success
• Deposit – The client will pass you a token and an amount of money to deposit into the user’s
Additionally, you need to think of and handle all possible error situations (such as: bad username-PIN
combinations and trying to withdraw more money than what you have).
I already implemented the database for you (in which does not need to be modified.
However, you do need to read the code, and familiarize yourself with how it works (a good place to start
is AccountDB::main – it demonstrates how the basic database operations work… you can also compile
the java file and run “java AccountDB” to see the output).
Out of the box, you can compile by using “javac ATMServer” (or “make” if you use the
Makefile), then run it by typing “java ATMServer”. In another window you can run “telnet
8080” and connect to your server. Type a line of text, and press enter. You see that the ATMServer
printed your message to the screen. Additionally, the server also sends the text back to the telnet client
and then closes the connection.
Another decision you must make is whether to keep the connection open between calls, or close the
socket connection after each command. This is entirely up to you.
In addition to implementing your protocol in the ATMServer class (again, please look for the TODO
comments), you MUST create your own custom client to connect to the server from scratch.
The Client (50% of your grade)
The client you will create (please name the class ATMClient) will use your new application layer protocol
to communicate with your ATMServer.
This client should be a text application that functions similarly to a conventional ATM. It should ask the
user for a username and PIN. Then, it should display a menu and allow the user to select commands. The
client should also print user friendly messages.
/ Tips
• Start early!
• Ask questions… ask them in the discussion on Canvas first before asking me.
• Help other students! Don’t give them your protocol, but feel free to collaborate via Canvas – I
will look at the discussions at the end of the semester and students who help other students
may get the benefit of the doubt if your grade is teetering on being a better grade
• The IP address of your server is
• The port of your server is 8080
• Make sure your server is running before you try to connect to it
• Install / use telnet to test out your server
• Only after you have your server working properly work on building the client
• There is a lot of code in your HTTP client from Assignment 1 that can be reused for building the
ATM client
• I have provided you a basic Makefile… this makes things simpler when compiling your program
/ Extra credit
• Alter the Makefile to build your client as well as the server
• Make a graphical client
• Use SSL
• In general, build something awesome that goes above and beyond and I’ll give you extra credit


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