On a Friday afternoon at work, I decided to challenge myself to go beyond framework-based development and dive deep into systems-level programming. To do that, I picked up a low-level HTTP server challenge by Codecrafters.io. This wasn’t just about building a server—it was about understanding the why and how behind every line of communication between a client and a server.

This post isn’t a tutorial. It’s a reflection on what I learned by building a fully functional HTTP/1.1 server from scratch in C++—handling raw sockets, multithreading, routing, compression, and persistent connections.

🌐 What This Project Involved

Raw TCP Socket Programming: I implemented server-side socket handling without any external HTTP libraries. This gave me a true appreciation for the foundation of web communication.
Routing & Request Parsing: I parsed raw HTTP requests to support custom endpoints like /echo/{msg}, /user-agent, and dynamic file serving under /files.
Persistent & Concurrent Connections: By default, HTTP/1.1 supports persistent connections. I used std::thread to handle multiple concurrent clients while managing individual request lifecycles.
Gzip Compression: I integrated gzip compression using zlib, sending compressed responses if the client specified Accept-Encoding: gzip. Implementing this involved a bit of byte-level manipulation and learning how compression actually works under the hood.
Testing with Curl & Debugging: Most of my debugging happened through curl and careful inspection of headers, hex dumps, and CRLF line endings.

🧠 What I Learned

How HTTP headers work and why they're crucial (especially things like Content-Length, Connection: close, Accept-Encoding, and User-Agent)
How to manage sockets manually in a Unix-like environment using POSIX APIs like socket, bind, listen, accept, recv and send
Why multithreading can be both powerful and error-prone
How to parse and construct HTTP/1.1 responses byte-for-byte
The importance of CRLF (\r\n) in HTTP spec compliance 😅

🤝 Credit Where It’s Due

This project was built as part of the Codecrafters HTTP Server challenge. They provide an excellent hands-on environment to learn by doing. Highly recommended if you are curious about how core software systems work behind the scenes.

📂 Project Link

👉 Check out the full code on GitHub
(Feel free to leave a ⭐ if you find it helpful or want to fork it!)

🎯 Final Thoughts

This experience reminded me why I love low-level programming. While it’s not always needed for day-to-day development, knowing what’s happening beneath the frameworks gives me more control and deeper understanding of performance, networking, and system behavior.

🚀 Building an HTTP Server from Scratch in C++: What I Learned