Concurrent Downloads and Uploads

Implemented forking processes for concurrent downloads and uploads for
Exercise 1. Updated answers.txt accordingly.
Upload Filepath Check

Ensured that uploaded files are within the current working directory for
Exercise 2B. Updated answers.txt accordingly.
Fixed Buffer Overflows

Fixed buffer overflow vulnerabilities for Exercise 2A. Updated
answers.txt accordingly.
Added Robustness

Added filename length checks and limited download sizes for Exercise 2B.
Updated answers.txt accordingly.