net.c

Purpose

This project is a learning journal of sorts, it started before my Data Structures course Spring of 26, and as I learn more I update this project with what I learned in/out of class whenever I have the time.

Update March 19th 2026

• Moved utility functions outside of net.c and into neth.c, and the prototype functions into neth.h as well as struct type and defines.
• Changed from singly linked list to dynamic array;
• Linked lists had caused memory fragmentation and cache misses because of the non-contiguous node allocation, while dynamic arrays are contiguous in memory, making iteration faster with better cache locality, and less per-element overhead.

Compilation:

I like to use gcc:

gcc -o net net.c neth.c

Basic usage:

 ./net -a : List all connections regardless of state.
 ./net -t : List connections with "ESTABLISHED" state.
 ./net -l : List connections with "LISTENING" state.

To be implemented:

Priority: get rid of get inode by pid function because the time complexity is horrendous, switching to hash table for constant/linear time complexity.

1. Better connection filtering and search by parsing dynamic command-line args. (optarg or getopt).
2. Live monitoring of /proc/net/tcp that updates every 2-3 seconds instead of a static capture.
3. DNS name resolution.
4. Export to JSON or CSV.
5. Maybe utilize eBPF in the future for faster captures.