CS18000 Programming Homework 10: External Communication


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Whether you realize it or not, servers, with the help of the internet, power our world. The
applications you used to access this handout, or post photos of your friends and family are all
powered by servers, and more specifically the client-server model.
In this model, a client sends a request to the server, and attempts to carry it out. The
“language” that the request must be in is often referred to as the protocol of the server. If the
request does not follow the protocol, it won’t be understood by the server.
Below you will implement a server that performs simple arithmetic, and can handle multiple
clients at the same time. You will have to parse each client’s request, and ensure that they
follow the proper protocol.
The following files have been provided as skeleton code:
➔ ArithmeticProtocol.java
➔ ArithmeticRequestHandler.java
➔ ArithmeticServer.java
➔ ArithmeticClient.java
A valid request to the server is a String of the form OPERATION NUM1 NUM2.
ArithmeticProtocol.java contains valid operation names, as well as a constant
representing an illegal request. If the request is illegal, you must send an error message back to
the client. These error messages have been declared for you as constants in the file
ArithmeticRequestHandler.java, which is where you will be completing this
In the file, you must implement the run() method, and interact with the client through the
clientSocket field. As long as the client keeps sending requests, you must keep the
connection open, and serve them to the best of your ability. You may use any I/O class that you
are comfortable with in order to communicate with the client, such as Scanner and
PrintWriter. Responses sent to the client must also be of type String. Example
interactions can be seen below.
ArithmeticServer.java and ArithmeticClient.java have also been provided,
and can help you test your implementation. Be sure to run ArithmeticServer.java first,
as the client must have a server to connect to.
Example Interactions
Request sent to the server: yo
Response sent to the client: ILLEGAL_REQUEST: requests must include an
operation name, and two operands all separated by spaces
Request sent to the server: yo 5 5
Response sent to the client: ILLEGAL_REQUEST: the operation name must be
part of the protocol
Request sent to the server: ADD Java 5
Response sent to the client: ILLEGAL_REQUEST: the first operand must be a
valid integer
Request sent to the server: SUBTRACT 53 var
Response sent to the client: ILLEGAL_REQUEST: the second operand must be a
valid integer
Request sent to the server: MULTIPLY 10 10
Response sent to the client: 100
Request sent to the server: DIVIDE 0 25
Response sent to the client: 0
You are required to complete one class, ArithmeticRequestHandler, that follows the
specifications outlined above. It is to be held in the file included in the skeleton code.
Submit all of the files to Vocareum through Blackboard. Keep in mind that only your latest
submission will be considered.
Grading Rubric
– ArithmeticRequestHandler class — 100 points total
– 5 points each
– Handles illegal requests
– Handles addition requests
– Handles subtraction requests
– Handles multiplication requests
– Handles division requests