HTTP from TCP

A minimal HTTP/1.1 server implementation built from scratch using raw TCP sockets in Go. This project demonstrates how to parse HTTP requests and write HTTP responses without using Go's standard net/http package.

Overview

This project implements a complete HTTP/1.1 server by:

• Parsing HTTP requests directly from TCP streams
• Managing HTTP headers and request bodies
• Writing properly formatted HTTP responses
• Supporting advanced features like chunked transfer encoding and trailers

Project Structure

.
├── cmd/
│   ├── httpserver/     # Full-featured HTTP server
│   └── tcplistener/    # Debug tool for inspecting HTTP requests
├── internal/
│   ├── headers/        # HTTP header parsing and management
│   ├── request/        # HTTP request parsing from TCP streams
│   ├── response/       # HTTP response writing
│   └── server/         # TCP server with connection handling
└── assets/
    └── vim.mp4         # Sample video file for testing

Features

• ✅ HTTP/1.1 Request Parsing: Complete request line, headers, and body parsing
• ✅ Streaming Parsing: Handles partial/incomplete data from TCP streams
• ✅ Chunked Transfer Encoding: Supports chunked responses with trailers
• ✅ Header Management: Case-insensitive headers with support for repeated headers
• ✅ Concurrent Connections: One goroutine per connection
• ✅ Graceful Shutdown: Proper cleanup on SIGINT/SIGTERM
• ✅ Error Handling: Comprehensive error handling with appropriate HTTP status codes

Building

# Build the HTTP server
go build -o httpserver ./cmd/httpserver

# Build the TCP listener (debug tool)
go build -o tcplistener ./cmd/tcplistener

Running

HTTP Server

./httpserver

The server listens on port 42069 by default.

TCP Listener (Debug Tool)

./tcplistener

This tool listens on port 42069 and prints parsed HTTP request information to stdout.

API Endpoints

The HTTP server (httpserver) implements the following routes:

• GET / - Returns a success HTML page (200 OK)
• GET /yourproblem - Returns 400 Bad Request
• GET /myproblem - Returns 500 Internal Server Error
• GET /httpbin/* - Proxies requests to httpbin.org with chunked encoding and trailers
  • Example: GET /httpbin/get proxies to https://httpbin.org/get
  • Returns chunked response with SHA256 hash in trailers
• GET /video - Serves the vim.mp4 file with proper video content type

Example Usage

# Test basic endpoint
curl http://localhost:42069/

# Test error endpoints
curl http://localhost:42069/yourproblem
curl http://localhost:42069/myproblem

# Test httpbin proxy
curl http://localhost:42069/httpbin/get

# Test video endpoint
curl http://localhost:42069/video -o output.mp4

Architecture

Request Parsing

The request parser uses a state machine to handle streaming data:

1. RequestStateInit: Parse the request line (method, target, version)
2. HeadersState: Parse HTTP headers
3. BodyState: Read body based on Content-Length header
4. RequestStateDone: Request fully parsed

Response Writing

The response writer enforces proper HTTP response structure:

1. Status Line: HTTP version, status code, and status text
2. Headers: HTTP headers (with support for chunked encoding)
3. Body: Response body (or chunked data)
4. Trailers: Optional trailer headers (for chunked encoding)

Headers

Headers are stored case-insensitively and support:

• Multiple values for the same header name
• Validation of header field names per RFC 7230
• Streaming parsing for incomplete data

Testing

Run the test suite:

go test ./...

The project includes comprehensive tests for:

• Header parsing with various edge cases
• Request parsing with different chunk sizes
• Body parsing with and without Content-Length

Implementation Details

• No net/http: All HTTP parsing and response writing is done manually
• Raw TCP: Uses net.Listen and net.Conn directly
• Streaming: Handles partial reads from TCP connections gracefully
• Concurrent: Each connection is handled in its own goroutine

License

This is a learning project demonstrating low-level HTTP implementation.