CS 4730

Project 1: HELLO-ACK Protocol

Get started writing asynchronous network code

Project 1: Hello-Ack

Introduction

You are to develop an asynchronous program that implements the protocol below. 

Hello-Ack Protocol

Each peer implements this protocol:

  1. Over a single UDP socket on the default port 50000: 

    1. Send an ASCII ‘HELLO’ message to all known peers (given on the command line)
    2. Send an ‘ACK’ message back to the source of every ‘HELLO’ message received

  2. Once a peer has received an ‘ACK’ from all known peers and sent an ACK in response to the HELLO messages from all its peers,

    1. If the node has the lowest IP address of all the peers, it prints “DONE: ” followed by a comma separated list of the “(domain name, IP address)” of the source of each of the received ‘ACK’ message
    2. Else, it prints only “DONE”

Your program should print exactly one line of output. Either “DONE” or “DONE:  [followed by the list specified above]”.
There must be NO extra debugging output, or you will lose points. 

Your program should have a deterministic result, i.e., it should always find the correct solution and none of the peers should crash. 

Your program

Your program, proj1, must execute on the command line using the following command.

$ ./proj1 [-h] --peers PEERS [PEERS ...] [--port PORT] [--timeout TIMEOUT] [--verbose]

--peers is required on the command line.
--port, --timeout, and --verbose must be implemented, but are optional on the command line.  

A Dockerfile and Docker Compose file, proj1-compose.yml, are supplied in the starter code.  While you may change either file, the evaluation will use the supplied Compose file.

To run and build the containers:
  • docker compose -f proj1-compose.yml up --build
To run the container after building:
  • docker compose -f proj1-compose.yml up

Asynchronous communication

We encourage you to write your code in an event-driven style, using select() or poll() on the datagram socket to which the peer is connected (see the starter code for an example). This will keep your code single-threaded, making debugging significantly easier. Alternatively, you can implement your router in a threaded model (with one thread handling each socket), but expect it to be substantially more challenging to debug.

Starter code

A template repository of fundamental starter code for the assignment in Python using Docker is available on the Khoury GitHub server. Provided is a simple implementation of a peer that opens a UDP socket, sends a HELLO message to its peers, and prints out every message it receives. You may use this code as a basis for your project if you wish.    

Submitting Your Project

Your Dockerfile, proj1-compose.yml, and source code, etc. should all be placed in the root directory of a compressed archive (i.e., a .zip file) and then uploaded to Gradescope.  Alternatively, you can check all these items into Khoury’s GitHub, download a zip file from Khoury’s GitHub, and submit that to Gradescope, or any other upload/submission option Gradescope permits.  If your submission is missing any required file for evaluation, it will receive 0 points.

There is NO autograder for this project.  Your submission will be evaluated by hand.  

Grading

The grading of this project will be broken down as follows:

Item Percentage of Grade
Program correctness 50%
Style and documentation 50%

Questions

Ask on Piazza or come to office hours (the TA’s or Prof. Jackson’s).

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