Homework 3 EXPERIMENTATION WITH NETWORKED COMMUNICATIONS

VERSION 1.0

The objective of this assignment is to get you to be comfortable coding in a networked setting where you need to manage the underlying communications between nodes. All communications will be based on TCP and you will be using the sockets to implement this assignment. The programming assignment should be implemented in Java. You are required to work alone on this assignment. The assignment accounts for 7.5% towards your cumulative course grade.

This assignment may be modified to clarify any questions (and the version number incremented), but the crux of the assignment and the distribution of points will not change. If there are any changes to the assignment, all changes will be documented in the “Change History” section of this assignment.



1    Description of Task


As part of this assignment, you will be responsible for designing programs that facilitate communications in a networked setting. Three machines will be involved during program execution. The programming assignment should be developed in Java version 8, and your classes must reside in the package “cs250.hw3”.

You will be designing two separate programs that implement functionality relating to key roles in the system: a server and a client.

Your server program will be provided with 3 arguments at the command line. The first argument specifies the port number that your server “listens” to. The second argument specifies the seed (an integer number) that is used to initialize the Server’s random number generator. The final argument, number-Of-Messages, specifies the number of messages that will be sent by each client that is connected to the server.

Server Command line compilation:
javac cs250/hw3/TCPServer.java

Server Command line execution format:
java cs250.hw3.TCPServer <port-number> <seed> <number-Of-Messages>

Server Command line execution example:
java cs250.hw3.TCPServer 1345 42 4


Your client program will be provided with 2 arguments at the command line. The two arguments specify the hostname and port-number where the Server is listening to for communications.









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CS250: FOUNDATIONS OF COMPUTER SYSTEMS
PROFESSOR: Shrideep Pallickara
Department of Computer Science

Colorado State University

Client Command line compilation:

javac cs250/hw3/TCPClient.java


Client Command line execution format:
java cs250.hw3.TCPClient <server-host> <server-port>

Client Command line execution example:
java cs250.hw3.TCPClient mars 1345


Note: the arguments checked must come from the “args” of the main method. Using the method “Scanner.nextLine()” (or a similar method) to read the numbers will result in a deduction.


1.1    Task 1: Server start-up

The server should first check to see if it is able to successfully create a server socket on the specified port. The value should be > 1024 <=65,535. You may encounter an exception if a server socket currently is bound to that port number, print that exceptions message using “exception.getMessage()”.

Upon start-up the server should initialize its random number generator using the specified seed provided.


1.2    Task 2: Registering two clients to the Server

Upon start-up the clients should first connect to the Server. Provided you have specified the correct server host/port information and the server is currently running this will result in a successful connection to the server.

The server should send 2 integers to the client.

The first integer specifies the number of messages that the server expects the client to send. This number is the argument that was specified to the server at its command line: you should not hard-code this number in your client-side code.

The second integer is a random number from the Server that is used to initialize the client-side random number generator. This will be the first random number that the server generates using its random number generator and the seed passed in through arguments.

Use the provided SubmissionOneClient to test your server code up to this point if you have not implemented a client yet.


1.3    Task 3: Sending messages from the client to the server

Now that the server has sent over 2 messages, the client should read these messages in the order they came in (First the number of messages, then the seed) and initialize its random number generator with the seed.

The client should now produce <numberOfMessages> amount of Integer numbers from the random number generator and send over each Integer to the server.

The client should also maintain a variable (long senderSum) which is used to maintain a running sum of all integer numbers that are being sent to the server. Setting this variable as a long allows you to circumvent any overflow situations that would arise if you used an int instead. Make sure to do this as overflow almost always happens.

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CS250: FOUNDATIONS OF COMPUTER SYSTEMS
PROFESSOR: Shrideep Pallickara
Department of Computer Science

Colorado State University


The client should maintain a second variable (int numOfSentMessages) that tracks the number of messages that were sent by the client.

Use the provided SubmissionTwoServer to test your client code up to this point if you have not implemented a complete server yet.


1.4    Task 4: Processing a message that is relayed from the server to the client

Now we will relay any messages from one client over to the other client.

Any message received by a server from a client (say A) will be relayed (or forwarded) to the other client (say B) that is connected to the server. So for each message client A sends to the server, the server is required to send that same message over to client B and vice versa with information from client B to client A.

The client should maintain a running sum of the messages received (or forwarded) by the server. This information is maintained in another variable (long receiverSum).

The client should also maintain a second variable (int numOfReceivedMessages) that tracks the number of messages that were received by the client from the server.

Note: You are sending the individual numbers generated from the random number generator, never are you sending the entire sum.


1.5    Task 5: Printing metadata information

This task entails printing metadata information at the server and the two clients.

In particular, the information that should be printed includes the number of messages and the running counts of the messages that are sent and received by each client.

This information is printed at the server and each of the clients. Printing this metadata information is what allows you to confirm the correctness of your implementation. The running counts should match up. For example:

    1. Let senderSum at client A be X

    2. Let the receiverSum at client B be Y. This receiverSum corresponds to messages from client A that were relayed by the server.
    3. If your implementation is correct then X=Y.  That is, what you sent is what was received!



2    What to Submit

Use the CS250 Canvas to submit a single .tar or .zip file that contains your Java source code, plus a

README.txt file. When the archive is opened, the directory structure should be as follows:

    • cs250
    o hw3
        ◦ TCPClient.java
        ◦ TCPServer.java
        ◦ Any other .java files needed for either program
        ◦ README.txt

The README.txt file must contain a description of each file submitted and any other information you feel that the TAs will need to grade your program.


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CS250: FOUNDATIONS OF COMPUTER SYSTEMS
PROFESSOR: Shrideep Pallickara
Department of Computer Science

Colorado State University



Other files (such as the “.class” files from compiling your code, or your “hw1” or “hw2” folders from the previous assignments) are allowed to be present and will be ignored.


Filename Convention: The archive file should be named as <FirstName>-<LastName>-HW3.tar. E.g., if you are Cameron Doe then the tar file should be named Cameron-Doe-HW3.tar. Note: Canvas sometimes adds an extra “-1”, “-2”, etc. to the file name, which is OK.

Tar File Command Format: tar -cf <FirstName>-<LastName>-HW3.tar cs250

Tar File Command Example: tar -cf Cameron-Doe-HW3.tar cs250

Zip File Command Format: zip -r <FirstName>-<LastName>-HW3.zip cs250

Zip File Command Example: zip -r Cameron-Doe-HW3.zip cs250

Note: we highly recommend using one of the commands above for creating your archive for submission. Creating an archive through your operating system’s GUI (or another GUI program) may not zip the file correctly, potentially resulting in a deduction on the assignment.



3    Grading

The assignments must compile and function correctly on machines in the CSB-120 Lab. Assignments that work on your laptop on your particular flavor of Linux, but not on the Lab machines are considered unacceptable.

This assignment will contribute a maximum of 7.5 points towards your final grade. The grading will also be done on a 7.5 point scale. There will be multiple submissions each building upon the previous for this assignment to ensure steady progress is made throughout the assignment duration. The points breakdown is as follows:

Points Breakdown

    • Submission One (2 points)

    • Submission Two (2 points)

    • Submission Three (3.5 points)






















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CS250: FOUNDATIONS OF COMPUTER SYSTEMS
PROFESSOR: Shrideep Pallickara
Department of Computer Science

Colorado State University




Submission One (2 points):

Tasks 1 and 2 should be completed. We will supply a compiled Client that can be used to connect to your server and will expect to receive one message with two integers. The first integer is the number of messages that the client should send back to the server. The second integer is the seed that should be used to initialize the client’s random number generator.

Example Outputs:

Success


Server (Neptune):

Command: java cs250.hw3.TCPServer 1345 42 4

IP Address: neptune/129.82.44.122

Port Number 1345

waiting for client...

Clients Connected!

Sending config to clients...

earth.cs.colostate.edu -1170105035

jupiter.cs.colostate.edu 234785527

Finished sending config to clients.

Client A (Jupiter):

Command: java SubmissionOneClient neptune 1345 Received config

number of messages = 4
seed = 234785527

Client B (Earth):

Command: java SubmissionOneClient neptune 1345 Received config

number of messages = 4
seed = -1170105035


Port already in use


Server (Neptune):

Command: java cs250.hw3.TCPServer 1345 42 4

IP Address: neptune/129.82.44.122

Port Number 1345

Address already in use (Bind failed)












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CS250: FOUNDATIONS OF COMPUTER SYSTEMS
PROFESSOR: Shrideep Pallickara
Department of Computer Science

Colorado State University




Submission Two (2 points):

Task 3 should be completed. We will supply a Server that your client will connect to. The server will send the client one message with two integers. The first integer is the number of messages that the client should send back to the server. The second integer is the seed that should be used to initialize the client’s random number generator. The client should then send that number of messages back to the server each containing one random integer. The client should maintain a count of messages sent along with the sum of the random numbers sent.

Example Output:


Server (Neptune):

Command: java cs250.hw3.SubmissionTwoServer 1345 42 30

IP Address: neptune/129.82.44.122

Port Number 1345

waiting for client...

Clients Connected!

Sending config to clients...

earth.cs.colostate.edu -1170105035

jupiter.cs.colostate.edu 234785527

Finished sending config to clients.

Starting to listen for client messages...

Finished listening for client messages.

earth.cs.colostate.edu

Messages received: 30

Sum received: -6382135587

jupiter.cs.colostate.edu

Messages received: 30

Sum received: -2496366311

Client A (Jupiter):

Command: java cs250.hw3.TCPClient neptune 1345 Received config

number of messages = 30
seed = 234785527
Starting to send messages to server...
Finished sending messages to server.
Total messages sent: 30

Sum of messages sent: -2496366311

Client B (Earth):

Command: java cs250.hw3.TCPClient neptune 1345 Received config

number of messages = 30

seed = -1170105035
Starting to send messages to server...
Finished sending messages to server.
Total messages sent: 30
Sum of messages sent: -6382135587

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CS250: FOUNDATIONS OF COMPUTER SYSTEMS
PROFESSOR: Shrideep Pallickara
Department of Computer Science

Colorado State University




Submission Three (3.5 points):

Task 4 and 5 should be completed. Your client and server should be compatible with our implementations meaning that given any combination of Client, Server task 4 and 5 should result in the same output given the same input arguments.

Example Output:


Server (Neptune):

Command: java cs250.hw3.TCPServer 1345 42 30

IP Address: neptune/129.82.44.122

Port Number 1345

waiting for client...

Clients Connected!

Sending config to clients...

earth.cs.colostate.edu -1170105035

jupiter.cs.colostate.edu 234785527

Finished sending config to clients.

Starting to listen for client messages...

Finished listening for client messages.

earth.cs.colostate.edu

Messages received: 30

Sum received: -6382135587

jupiter.cs.colostate.edu

Messages received: 30

Sum received: -2496366311

Client A (Jupiter):

Command: java cs250.hw3.TCPClient neptune 1345 Received config
number of messages = 30
seed = 234785527
Starting to send messages to server...
Finished sending messages to server.
Total messages sent: 30

Sum of messages sent: -2496366311
Starting to listen for messages from server...
Finished listening for messages from server.
Total messages received: 30
Sum of messages received: -6382135587


Client B (Earth):

Command: java cs250.hw3.TCPClient neptune 1345 Received config

number of messages = 30
seed = -1170105035
Starting to send messages to server...


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CS250: FOUNDATIONS OF COMPUTER SYSTEMS
PROFESSOR: Shrideep Pallickara

Department of Computer Science


Colorado State University





Finished sending messages to server.


Total messages sent: 30


Sum of messages sent: -6382135587


Starting to listen for messages from server...


Finished listening for messages from server.


Total messages received: 30


Sum of messages received: -2496366311




Deductions:

1 points each for not following the prescribed argument specification.

3 points for hardcoding any values in the system; everything should be argument driven including the random number generator.

You are required to work alone on this assignment.



4    Late Policy

Please check the class policy on submitting late assignments. You are allowed to submit assignments up to 24 hours late with a 7.5% deduction, or up to 48 hours late with a 15% deduction.





5    Version Change History

This section will reflect the change history for the assignment (if needed) after the first public release of the assignment. It will list the version number, the date it was released, and the changes that were made to the preceding version. Any changes to the first public release are made to clarify the assignment; the spirit or the crux of the assignment will not change.


Version

Date

Comments


























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