CS2105 Assignment 2 Solved

We will test and grade your program on the sunfire server. Please make sure that your program run properly on sunfire. Moreover, you are allowed to use libraries installed in public folders of sunfire (e.g. /usr/lib) only.

We accept submission of Python 3 (in particular, 3.7), Java, or C/C++ program, and we recommend that you use Python 3 for your assignments. Programming languages other than Python 3, Java, and C/C++ are not allowed. For Python 3, we use the python3 program installed in folder /usr/local/Python-3.7/bin on sunfire for grad- ing. If you use Java or C/C++, we will compile and run your program for grading using

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the default compilers on sunfire (java 9.0.4 installed in /usr/local/java/jdk/bin, or gcc 4.8.4 installed in /usr/local/gcc-4.8/bin). The grading script infers your programming language from the file extension name (.py, .java, .c). Therefore, please ensure your files have the correct extension names. For a Java program, the class name should be consistent with the source file name, and please implement the static main() method so that the program can be executed as a standalone process after compilation. We will deduct 1 mark for every type of failure to follow instructions (e.g. wrong program name).

Note that for Java programs, name your main class as Server/Client and hence source file name Server.java/Client.java during development. When you want to test your pro- gram using the provided script on Sunfire, or to make submission, rename your file name according to program submission and group submission section while keeping the class name as Server/Client. Grading script will rename your file accordingly during compilation.

We will grade your program based on its correctness only. A grading script will be used to test your program and no manual grading will be provided.

Program Submission

Forindividualsubmission,pleasenameyourtwosourcefileasServer-<Matric number>.py andClient-<Matric number>.py;andsubmititinasinglezipfile<Matric number>.zip,
to the Assignment_2 folder of LumiNUS Files.

Here, <Matric number> is your matriculation number which starts with letter A. An ex- ample file name would be Server-A0165432X.py. If you use Java, C, or C++ to im- plement the web server, please use .java, .c, or .cpp respectively as the extension name. Note that file names are case-sensitive on sunfire.

You are not allowed to post your solutions to any publicly accessible site on the Internet.

Special Instructions for Group Submission

For group submission, please include matriculation numbers of both students in the file name, i.e. Server-<Matric number 1>-<Matric number 2>.py. Submit it to the same Assignment_2 folder. An example file name would be Client-A0165432X-A0123456Y. py. For each group, there should be one designated member who submits the file, to avoid problems caused by multiple branches within a group. Do not change the designated submitter! If the group needs to upload a new version, it should be done by the same designated submitter as well.

Plagiarism Warning

You are free to discuss this assignment with your friends. However, you should refrain from sharing your program, program fragments, or detailed algo with others. If

rithms

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you want to solve this assignment in a group, please do so and declare it as group work.

We employ zero-tolerance policy against plagiarism. If a suspicious case is found, student would be asked to explain his/her code to the evaluator in face. Confirmed breach may result in zero mark for the assignment and further disciplinary action from the school.

Question & Answer

If you have any doubts on this assignment, please post your questions on Piazza fo- rum before consulting the teaching team. However, the teaching team will NOT debug programs for students and we provide support for language-specific questions as a best-effort service. The intention of Q&A is to help clarify misconceptions or give you necessary directions.

FAQ

We will collate your questions here: link

The Unreliable Channel

We have implemented 3 simulators on the machine 137.132.92.111, to mimic unreli- able channels. Your server and client have to connect to any simulators and transfer files.

• The simulator waits for both the client and server to connect the simulator via TCP connection before enabling the channel.
• The architecture can be found in fig:1
• Task
  • –  connect to the simulator with a handshake. The handshake is similar to As- signment 1, with an extra character C to signify client and S to signify server. The handshake details can be found in fig:2
  • –  The simulator will send you the current waiting list number; you need to wait till you receive 0_. We allow only 10 students to connect to a simulator at any given time.
  • –  Then you transfer file from the server to the client. The input file will be provided as command line parameter to the server
  • –  Save the received file to the file name provided to client as command line parameter
• You earn 1 mark per correct file transfer in the case of Reliable Channel.
• You earn 2 mark per correct file transfer in the case of other channels.

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• Forgot to mention; the simulator really hates making friends. It will timeout and terminate in a fixed time. It is set to 100 Sec now, but will be progressively reduced based on the statistics we collect.

Figure 1: Architecture.

Figure 2: Handshake FSM.

Let us understand the Simulator further:
• All the simulators have the following constraints

– The packet size from the server is fixed to 1024 B. – The packet size from the client is fixed to 64 B.
– Partial packets will not be delivered
– No packets will be dropped

• The 3 Simulators are:

• –  Reliable Channel (Mode 0): This channel introduces no error or reorderingof packets. Fig 3
• –  Error Channel (Mode 1): This channel introduces errors in packets. Fig 4
• –  Reordering Channel (Mode 2): This channel reorders packets. Fig 5

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Figure 3: Reliable channel FSM.

Figure 4: Error channel FSM.

Testing Your Program

To test your program, please use your SoC UNIX ID and password to log on to sunfire as instructed on Assignment_0.

• Since you have 2 programs, you will be running them on 2 separate terminals
• Yourprogramshouldreceivefivecommand-lineargumentasthefollowingcom-mand shows:

  python3 Sever-A0165432X.py <student_key> <mode> <ip_address> <port_num> <input_ file_name>

  python3 Client-A0165432X.py <student_key> <mode> <ip_address> <port_ num> <output_file_name>

  – <student_key>: The 6 digit key is the same as the one used in Assignment_1.
  – <mode>: Is the integer input corresponding to the simulator we are connecting to – <ip_address>: The IP address of the machine on which the simulator is running. – <port_num>: The port number of the TCP socket corresponding to the simulator. – <input_file_name>: The file to be transferred
  – <output_file_name>: The destination file name

• During the evaluation, we will change the input files, the IP address and the port number; hence your code should accept all the above mentioned command line parameters.
• Note that your program should not read from stdin. Your program can print any- thing to stdout or stderr, and our test script will silently ignore them.
• We also release a set of grading scripts to you under the test folder.

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Figure 5: Reorder channel FSM.

• To use the grading script, please upload your program along with the test folder given in the package to sunfire. Ensure that your program and the test folder are in the same directory. You can run the following command for help:

bash test/FileTransfer.sh -h
• To run the test script for server, kindly use the -s option

All of you will be connection to a single server, hence start the assignment early to avoid “congestion” during last few days.

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