HTTP Server from Scratch

Building an HTTP server from scratch in Go to understand operating systems, networking, and the HTTP protocol at a fundamental level.

What This Project Is

A learning project where I'm implementing an HTTP server without using high-level frameworks. Starting from raw TCP sockets and building up to handle HTTP requests and responses.

What I'm Learning

Operating Systems & Networking

• Socket file descriptors — How the OS manages network connections as file descriptors
• Listener vs connection FDs — The difference between the listening socket (accepts connections) and connection sockets (read/write data)
• TCP connections — How clients and servers establish connections with ephemeral ports
• Port ranges — Well-known (0-1023), registered (1024-49151), and ephemeral (49152-65535)

HTTP Protocol

• Request format — Parsing raw HTTP requests with \r\n line endings
• Headers and body — Splitting headers from body using \r\n\r\n
• Request methods — GET, POST, etc.
• Response format — Status lines, headers, and body

Go Concepts

• Package structure — package main (programs) vs library packages
• Testing — Test files in the same package to access unexported functions
• Error handling — Proper nil checking before calling methods
• Defer — Cleanup only happens if the defer statement is reached

Architecture

main.go          → Entry point, starts server
server/          → Server logic (listener, connection handling)
├── server.go    → Server struct and methods
└── parser.go    → HTTP request parsing

Running

make run
# or
go run .

Testing

curl -v http://localhost:5100/

Roadmap

1. ✅ Set up listener socket and accept connections
2. ✅ Read raw bytes from connection
3. ⏳ Parse HTTP request (method, path, headers, body)
4. ⏳ Build response writer
5. ⏳ Implement router
6. ⏳ Handle incomplete reads and keep-alive connections