Event-Driven HTTP Server in C

A high-performance, memory-safe HTTP/1.0 server built from scratch using an epoll-based event loop inspired by nginx.

This project is built based on the HTTP/1.0 RFC spec written. It currently only has implemented GET,PUT and HEAD. All code is memory safe as per extensive testing. It was validated using valgrind.

This project was built to:

• Explore low-level systems programming in C
• Implement a memory-safe HTTP parser from scratch
• Design a scalable event-driven architecture using epoll
• Understand tradeoffs vs thread-per-request models

Design Decisions & Tradeoffs

Why epoll over threads?

I chose an epoll-based event-driven model over a thread-per-request architecture to better handle high concurrency with lower resource overhead. Threaded models are simpler but scale poorly due to memory usage and context-switching costs. In contrast, epoll enables a non-blocking, single-threaded design that efficiently manages thousands of concurrent connections with minimal overhead. The tradeoff is increased implementation complexity (state management, partial I/O handling), but it proved to be a good learning experience :D

How the event driven loop works

• Each process listens on the same port using SO_REUSEPORT. (Using epoll over comes the thundering herd problem)
• Once a connection is made, the process makes a new non-blocking connect socket and add its to the interest list for epoll and waits for IO again.
• When some data is written to a connection socket, we process it, and map the response for it, to each particular socket. I.E each connection socket will have a processed return request mapped to it.
• Then when the socket is ready for read, we write the mapped response to it and close it.

What I Learned

• How real-world servers like nginx work internally
• Tradeoffs between concurrency models
• Writing safe systems code in C, and validating the same using valgrind.
• Designing state machines for streaming protocols

Future Plans

• Caching for repeat requests.
• Extend functionality for DELETE, POST.
• Include Cookie based authentication, and Gzip-encoding.

How to build and Run

You can use any generator you want but this project is only written for Unix systems right now.

Build

cmake -S . -B build -G "Unix Makefiles"
cd build
make

Run

For server

./http1 server

For client

./http1 client "GET url HTTP/1.0\r\n"