For my cybersecurity masters work, I wanted to go deeper than running tools and reading packet captures. I wanted to understand what was happening inside the packets themselves. Instead of calling Scapy or hiding behind Python abstractions, I decided to build my own packet manipulation library from scratch in Nim. That became NimPacket, and it turned out to be one of the most useful and eye opening projects I have done.
NimPacket gives full control of IPv4, TCP, UDP, and ICMP headers. Everything is exposed at the byte level. You can set fields, flip flags, stack layers, serialize to raw bytes, and then parse real traffic back into readable structures. Working at this depth made me understand not just how protocols work but how they fail and how attackers take advantage of them.
I included real examples so the library is not just a research exercise. There is a working SYN port scanner, a raw packet sniffer, and an ICMP echo builder. These examples helped validate the code and also give anyone reading the repository a clear idea of how to apply the library in actual security work. It runs smoothly on Kali and makes it easy to build custom packet tools without relying on heavy frameworks.
The project taught me a lot about checksum algorithms, endian handling, field packing, and protocol specifications. It also showed me why low level networking is still important for people in cybersecurity. You cannot fully understand network attacks unless you know what each byte represents and why it is there.
If you want to see the code or try it out, the repository is here:
https://github.com/0x57Origin/NimPacket
I am always open to feedback from people who have more experience in systems programming or raw socket work, so feel free to check it out and let me know what you think.
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