HTTP Server From Scratch

A high-performance, concurrent HTTP/1.1 server implementation in Go, built from the ground up following RFC 2616 specifications. This project demonstrates deep understanding of network programming, TCP/IP protocols, and Go's concurrency patterns.

🚀 Key Features

• HTTP/1.1 Protocol Implementation: Adheres to core aspects of the HTTP/1.1 specification (RFC 2616).
• Concurrent Request Handling: Leverages Go's concurrency model (goroutines) to efficiently handle multiple client connections simultaneously.
• Custom Router: Implements a basic but effective path-based routing system to direct requests to appropriate handlers.
• RESTful Endpoints: Provides several standard endpoints:
  • GET /: Basic health check.
  • GET /echo/{message}: Echoes back the provided message in the response body.
  • GET /user-agent: Returns the client's User-Agent header value.
  • GET /files/{filename}: Serves static files from a specified directory.
  • POST /files/{filename}: Allows clients to upload files to the server's specified directory.
• Static File Serving & Upload: Capable of serving existing files and accepting file uploads with appropriate Content-Type handling.
• Header Parsing: Correctly parses HTTP request headers, including User-Agent, Content-Length, Content-Type, and Connection.
• HTTP Compression: Supports gzip compression based on the Accept-Encoding request header.
• Robust Error Handling: Returns appropriate HTTP status codes (e.g., 200 OK, 201 Created, 404 Not Found, 500 Internal Server Error) and informative error messages.

🛠️ Technology Stack

• Language: Go (Golang)
• Testing: Go testing package
• Network: Native Go TCP/IP stack
• Protocols: HTTP/1.1
• Core Libraries: Go Standard Library (net, bufio, os, fmt, strings, sync, compress/gzip)

🏗️ Architecture

The project follows clean architecture principles with clear separation of concerns:

├── app/
│   ├── main.go          # Entry point
│   └── main_test.go     # Integration tests
├── internal/
│   ├── handlers/        # Request handlers
│   ├── protocol/        # HTTP protocol implementation

📥 Installation

Follow these steps to get the server running on your local machine.

Prerequisites:

• Go (Version 1.18+ Recommended)
• Git (for cloning the repository)

Steps:

1. Clone the repository:

   git clone https://github.com/md-talim/codecrafters-http-server-go.git
   # Or: git clone [Your Fork URL]

2. Navigate to the project directory:

   cd codecrafters-http-server-go

3. Build the application:

   go build -o http-server-go ./app/main.go

   This will create an executable file named http-server-go (or http-server-go.exe on Windows) in the current directory.

4. Environment Variables:

   • No specific environment variables are required for basic operation. Configuration is primarily handled via command-line arguments (see Configuration).

5. Run the application:

   ./http-server-go [--directory /path/to/serve/files]

   • Replace /path/to/serve/files with the actual directory you want the server to use for file operations (GET/POST /files/...). If omitted, file operations might default to the current working directory or be disabled depending on implementation details.
   • The server will start listening on 0.0.0.0:4221.

🚦 Usage

Once the server is running, you can interact with it using an HTTP client like curl or a web browser.

• Health Check:

  curl -v http://localhost:4221/

  Expected Response: HTTP/1.1 200 OK

• Echo Service:

  curl -v http://localhost:4221/echo/hello-world

  Expected Response: HTTP/1.1 200 OK with hello-world in the body.

• User-Agent:

  curl -v --header "User-Agent: foobar/1.2.3" http://localhost:4221/user-agent

  Expected Response: HTTP/1.1 200 OK with foobar/1.2.3 in the body.

• Get File (Requires --directory flag during startup):

  # Assuming a file named 'example.txt' exists in the specified directory
  curl -v http://localhost:4221/files/example.txt

  Expected Response: HTTP/1.1 200 OK with the content of example.txt.

• Upload File (Requires --directory flag during startup):

  curl -v --data "This is the file content." http://localhost:4221/files/newfile.txt

  Expected Response: HTTP/1.1 201 Created

• Not Found:

  curl -v http://localhost:4221/nonexistent-path

  Expected Response: HTTP/1.1 404 Not Found

🧪 Testing

Run the test suite:

go test ./app

📖 Learning Resources

This project was built as part of the "Build Your Own HTTP Server" challenge from CodeCrafters. Key learning resources:

• RFC 2616 - HTTP/1.1
• Go Net Package Documentation

🙏 Acknowledgements

• CodeCrafters for the project challenge and structure
• The Go team for excellent networking primitives and documentation