HTTPfromTCP

Building HTTP/1.1 from TCP in Go

HTTPfromTCP is an educational project that explores the fundamentals of web networking by implementing the HTTP/1.1 protocol directly on top of raw TCP sockets in Go. By deliberately avoiding Go’s high-level net/http abstractions, this project demonstrates how HTTP is structured, parsed, and transmitted at the network level.

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Project Overview

Modern web servers hide most protocol details behind frameworks and libraries. This project removes those abstractions and rebuilds HTTP/1.1 from the ground up on top of TCP. The goal is to gain a precise, implementation-level understanding of how browsers and servers communicate.

Key learning areas include:

• TCP connection handling
• HTTP request/response parsing
• HTTP/1.1 features such as Keep-Alive and chunked transfer encoding
• Streaming data over long-lived connections

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Key Features

TCP-Based Communication

• Implements a web server directly on top of TCP sockets.
• No use of net/http for request parsing or response writing.
• Demonstrates how raw byte streams are converted into structured HTTP messages.

Concurrent Request Handling

• Each incoming TCP connection is handled independently.
• Supports multiple simultaneous clients without blocking.
• Demonstrates real-world server concurrency patterns.

HTTP/1.1 Compliance

• Implements persistent (Keep-Alive) connections.
• Supports chunked transfer encoding, enabling streaming responses.
• Compatible with modern web browsers.

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Technical Implementation

Custom Request Parsing

• Manually parses:
  • Request line (method, path, version)
  • Headers (case-insensitive handling)
  • Optional request bodies
• Operates directly on raw byte streams from the TCP connection.

Chunked Transfer Encoding

• Writes HTTP responses using chunked encoding.
• Correctly terminates chunks and sends trailers.
• Supports custom trailer headers such as X-Content-SHA256.

Proxy Capabilities

• Includes a ProxyHandler that:
  • Forwards incoming requests to external services (e.g., httpbin.org)
  • Streams the upstream response back to the client
• Demonstrates bidirectional streaming over TCP.

Routing & Status Handling

• Custom routing logic for paths such as:
  • /video
  • /yourproblem
• Handles standard HTTP status codes:
  • 200 OK
  • 400 Bad Request
  • 500 Internal Server Error

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Project Structure

.
├── cmd/
│   ├── httpserver/
│   │   └── main.go        # Full HTTP/1.1 server implementation
│   └── tcplistener/
│       └── main.go        # Minimal TCP listener for raw request logging
├── internal/
│   ├── request/           # HTTP request parsing logic
│   ├── response/          # HTTP response construction and writing
│   └── headers/           # Case-insensitive header handling and validation

Getting Started

Prerequisites

• Go 1.20 or later (recommended)

Run the HTTP Server

• Start the server on port 42069:

go run cmd/httpserver/main.go

• Then open a browser and visit:

http://localhost:42069

• You can also test using curl:

curl -v http://localhost:42069/