CS_421_Computer_Networks

This repository contains the homeworks that I did for Bilkent CS421 Computer Networks Course.

• Homework 1 : Wireshark Assignment
  • Description: In this homework assignment, we were asked to investigate application layer protocols such as HTTP and DNS by using packet analyzing sofwtare Wireshark. In HTTP, I analyzed basic HTTP get/response interactions, HTTP conditional get/response interactions, retriving long documents, HTML documents with embedded objects and HTTP authentication by examining the packets captured. I have examined the HTTP request/response messages, their contents, their status' and codes, the IP addresses of the destined messages and so on. In DNS, I have analyzed nslookup and ipconfig commands, and I have also used Wireshark for tracing DNS. I have examined the DNS queries, their contents, their types, the IP addresses of DNS servers.
• Programming Assignment 1 : Proxy Downloader
  • Description: In this programming assignment, we were asked to develop a program in either Java or Python which downloads files using HTTP commands and implements a proxy server. In the first part of the assignment I have used Netcat working tool to analyze the HTTP request messages that a proxy server receives. In the second part, I have developed a program in Java which prints the HTTP "GET" messages that the browser(Firefox) is sending using a proxy server. The program retrieves the content of the requested file and it downloads it as long as user visits websites.
    How to run:
    1. Compile: “javac ProxyDownloader.java”
    2. Run: “java ProxyDownloader ” command.