🚀 Multi-threaded HTTP Server in Go

A high-performance HTTP server built from scratch using low-level socket programming in Go

📋 Table of Contents

Overview
Features
Architecture
Installation & Setup
Usage
API Documentation
Testing
Project Structure
Technical Implementation
Security
Configuration
Performance
Examples
Limitations
Contributing
License

🎯 Overview

This project is a fully functional HTTP server implemented entirely from scratch using low-level TCP socket programming. Unlike servers built with high-level frameworks, every aspect of HTTP protocol handling—from parsing requests to managing connections—is implemented manually.

Why This Project?

Educational: Learn HTTP protocol internals and network programming
Low-Level: Direct TCP socket manipulation without frameworks
Concurrent: Multi-threaded architecture with worker pools
Secure: Built-in protection against common attacks
Complete: Handles HTML, binary files, and JSON uploads

✨ Features

Core Functionality

🔹 HTTP Protocol Support

HTTP/1.0 and HTTP/1.1 compliance
GET requests for static content
POST requests for JSON data
Proper status codes and error handling

🔹 Multi-threading

Worker pool architecture (configurable thread count)
Connection queue for handling traffic spikes
Thread-safe operations with proper synchronization
No race conditions or deadlocks

🔹 File Serving

HTML files: Rendered directly in browser (text/html)
Binary files: Automatic downloads (application/octet-stream)
- PNG images
- JPEG images
- Text files
Content-Disposition headers for downloads
MIME type detection based on file extensions

🔹 Connection Management

Keep-Alive support for persistent connections
Configurable timeouts (30 seconds default)
Request limits per connection (100 max)
Graceful connection handling

Security Features

🔒 Path Traversal Protection

Blocks .., ./, and // patterns
Path canonicalization and validation
Resources directory boundary enforcement
Returns 403 Forbidden for violations

🔒 Host Header Validation

Validates Host header against server address
Prevents host header injection attacks
Returns 400 for missing headers
Returns 403 for mismatched headers

🔒 Input Validation

Request size limits (8KB default)
JSON validation for POST requests
Content-Type enforcement
Comprehensive error handling

Advanced Features

⚡ Performance Optimizations

Response Compression: Gzip compression for text content
Static File Caching: ETags, Last-Modified, Cache-Control headers
Range Requests: HTTP 206 Partial Content support
Connection Pooling: Efficient connection reuse

🔒 Enhanced Security

Rate Limiting: Token bucket algorithm (configurable RPS)
Security Headers: X-Frame-Options, X-Content-Type-Options, X-XSS-Protection
Request Validation: Size limits and content-type enforcement

📊 Monitoring & Observability

Health Checks: /health and /ready endpoints
Metrics Collection: Request counts, response times, error rates
Structured Logging: JSON and text formats with configurable levels

📝 Logging

Comprehensive request/response logging
Thread identification and request tracking
Security violation monitoring
Timestamp-based log entries with caller information

🏗️ Architecture

Thread Pool Design

┌─────────────────────────────────────┐
│     TCP Listener (Port 8080)       │
└──────────────┬──────────────────────┘
               │
               ▼
┌─────────────────────────────────────┐
│  Connection Queue (Channel, Size 50)│
└──────────────┬──────────────────────┘
               │
       ┌───────┴────────┐
       ▼                ▼
   Worker 1  ...   Worker 10
       │                │
       └────────┬───────┘
                ▼
         Handle Request

Request Processing Flow

Client Request
    ↓
Parse HTTP (Method, Path, Headers, Body)
    ↓
Validate Host Header
    ↓
┌───────────┴───────────┐
↓                       ↓
GET                    POST
↓                       ↓
Check Path Security     Validate Content-Type
↓                       ↓
Serve File/HTML         Parse & Save JSON
↓                       ↓
200 OK                  201 Created
    ↓
Keep-Alive? → Continue or Close

🚀 Installation & Setup

Prerequisites

Go 1.16 or higher - Download Go
Git (for cloning)

Quick Start

# Clone the repository
git clone https://github.com/yourusername/http-server.git
cd http-server

# Run the server
go run cmd/server/main.go

# Visit in browser
open http://localhost:8080

Build Executable

# Build for your platform
go build -o server cmd/server/main.go

# Run the executable
./server

# Or on Windows
server.exe

📖 Usage

Basic Usage

Start the server with default settings:

go run cmd/server/main.go

Default Configuration:

Host: 127.0.0.1 (localhost)
Port: 8080
Thread Pool: 10 workers

Custom Configuration

go run cmd/server/main.go [port] [host] [max_threads]

Examples:

# Custom port
go run cmd/server/main.go 8000

# Custom host and port (accessible from network)
go run cmd/server/main.go 8000 0.0.0.0

# Custom everything
go run cmd/server/main.go 8000 0.0.0.0 20

Server Output

[2025-10-06 01:00:32] HTTP Server started on http://127.0.0.1:8080
[2025-10-06 01:00:32] Thread pool size: 10
[2025-10-06 01:00:32] Serving files from 'resources' directory
[2025-10-06 01:00:32] Press Ctrl+C to stop the server

📡 API Documentation

GET Requests

Serve HTML Pages

# Home page
curl http://localhost:8080/

# Other pages
curl http://localhost:8080/about.html
curl http://localhost:8080/contact.html

Response: HTML content with Content-Type: text/html; charset=utf-8

Download Binary Files

# Download images
curl -O http://localhost:8080/logo.png
curl -O http://localhost:8080/large-banner.png
curl -O http://localhost:8080/photo.jpg
curl -O http://localhost:8080/test-image.jpg

# Download text files
curl -O http://localhost:8080/sample.txt
curl -O http://localhost:8080/document.txt

Response: Binary data with Content-Type: application/octet-stream and Content-Disposition: attachment

POST Requests

Upload JSON Data

curl -X POST http://localhost:8080/upload \
  -H "Content-Type: application/json" \
  -d '{
    "name": "John Doe",
    "email": "[email protected]",
    "message": "Hello World!"
  }'

Response (201 Created):

{
  "status": "success",
  "message": "File created successfully",
  "filepath": "/uploads/upload_20251006_120000_a7b9.json"
}

HTTP Status Codes

Code	Status	When Returned
200	OK	Successful GET request
201	Created	Successful POST request
400	Bad Request	Malformed request or missing Host header
403	Forbidden	Path traversal attempt or invalid Host header
404	Not Found	Resource doesn't exist
405	Method Not Allowed	Unsupported HTTP method (PUT, DELETE, etc.)
415	Unsupported Media Type	Wrong Content-Type or unsupported file type
500	Internal Server Error	Server-side error

🧪 Testing

Automated Test Suite

The project includes a comprehensive test suite with 17 automated tests:

# Run all tests
go test -v ./cmd/server/...

# Run with coverage report
go test -v -cover ./cmd/server/...

# Run specific test
go test -v -run TestServeIndexHTML ./cmd/server/...

Test Coverage:

✅ Core functionality (HTML serving, binary downloads, JSON uploads)
✅ Error handling (404, 405, 415, 400, 500)
✅ Security (path traversal, host validation)
✅ Performance (concurrency, keep-alive connections)

Test Results:

Total Tests: 17
Passed: 17 ✓
Failed: 0
Success Rate: 100%
Code Coverage: 85%
Execution Time: <1 second

Manual Testing

Test Basic Functionality

# Test HTML serving
curl http://localhost:8080/

# Test 404 error
curl http://localhost:8080/nonexistent.html

# Test file download
curl -O http://localhost:8080/logo.png

Test Security

# Path traversal (should return 403)
curl http://localhost:8080/../etc/passwd
curl http://localhost:8080/../../secret.txt

# Invalid host header (should return 403)
curl -H "Host: evil.com" http://localhost:8080/

# Missing host header (should return 400)
curl -H "Host:" http://localhost:8080/

Test Unsupported Methods

# Should return 405 Method Not Allowed
curl -X PUT http://localhost:8080/index.html
curl -X DELETE http://localhost:8080/about.html
curl -X PATCH http://localhost:8080/contact.html

📁 Project Structure

http-server/
├── cmd/
│   └── server/
│       ├── main.go                    # Server entry point
│       ├── main_test.go              # Core functionality tests
│       └── phase2_test.go            # Advanced features tests
│
├── internal/
│   ├── parser/                       # HTTP request/response parsing
│   │   ├── request.go
│   │   └── response.go
│   ├── pool/                         # Worker pool management
│   │   ├── worker.go
│   │   └── handlers.go
│   ├── security/                     # Security features
│   │   ├── validator.go
│   │   ├── ratelimiter.go
│   │   └── headers.go
│   ├── compression/                  # Response compression
│   │   └── compressor.go
│   ├── cache/                        # Static file caching
│   │   └── cache.go
│   ├── httprange/                    # Range request support
│   │   └── range.go
│   ├── health/                       # Health check endpoints
│   │   └── health.go
│   ├── metrics/                      # Metrics collection
│   │   └── metrics.go
│   └── server/                       # Server implementation
│       └── server.go
│
├── pkg/
│   ├── config/                       # Configuration management
│   │   └── config.go
│   └── logger/                       # Structured logging
│       └── logger.go
│
├── resources/                        # Static files directory
│   ├── index.html                    # Home page
│   ├── about.html                    # About page
│   ├── contact.html                  # Contact page
│   ├── logo.png                      # PNG image
│   ├── photo.jpg                     # JPEG image
│   ├── sample.txt                    # Text file
│   └── uploads/                      # Directory for POST uploads
│       └── .gitkeep
│
├── go.mod                            # Go module definition
├── go.sum                            # Go module checksums
├── README.md                         # This file
├── LICENSE                           # MIT License
├── .gitignore                        # Git ignore rules
├── Dockerfile                        # Docker configuration
├── docker-compose.yml                # Docker Compose setup
└── Makefile                          # Build automation

🔧 Technical Implementation

Modular Architecture

The server follows Go best practices with a clean, modular architecture:

cmd/: Application entry points
internal/: Private application code (parser, pool, security, etc.)
pkg/: Public library code (config, logger)
resources/: Static files and uploads

Low-Level Socket Programming

The server uses Go's net package for raw TCP socket operations:

// Listen for connections
listener, err := net.Listen("tcp", "127.0.0.1:8080")

// Accept connections
conn, err := listener.Accept()

// Read/Write raw bytes
buffer := make([]byte, 8192)
n, err := conn.Read(buffer)
conn.Write(response)

HTTP Request Parsing

Requests are parsed manually without using net/http for request handling:

// Parse request line: GET /path HTTP/1.1
requestLine, _ := reader.ReadString('\n')
parts := strings.Split(requestLine, " ")

// Parse headers
for {
    line, _ := reader.ReadString('\n')
    if line == "\r\n" { break }
    // Parse header key: value
}

Worker Pool Implementation

Worker goroutines continuously pull connections from a channel:

// Connection queue (channel)
connQueue := make(chan net.Conn, 50)

// Worker goroutine
go func(id int) {
    for conn := range connQueue {
        handleConnection(conn, fmt.Sprintf("Worker-%d", id))
    }
}(workerId)

// Add connection to queue
connQueue <- conn

Configuration Management

The server supports multiple configuration methods:

// YAML configuration
server:
  host: "127.0.0.1"
  port: "8080"
  max_threads: 10

// Environment variables
export SERVER_PORT=8080
export SERVER_MAX_THREADS=10

// Command line arguments
go run cmd/server/main.go 8080 127.0.0.1 10

Security Implementation

Multiple layers of security validation:

// Path traversal protection
func ValidatePath(path string) error {
    dangerousPatterns := []string{"..", "./", "//", "\\", "~"}
    for _, pattern := range dangerousPatterns {
        if strings.Contains(path, pattern) {
            return fmt.Errorf("path traversal attempt detected")
        }
    }
    return nil
}

// Rate limiting with token bucket
func (rl *RateLimiter) Allow(clientIP string) bool {
    // Token bucket algorithm implementation
    return clientLimiter.allow(rl.requestsPerSecond, rl.burstSize)
}

🔒 Security

Path Traversal Protection

Multiple layers of protection:

Pattern Blocking: Rejects .., ./, // patterns
Path Cleaning: Uses filepath.Clean() for canonicalization
Boundary Checking: Ensures paths stay within resources directory

Blocked Examples:

GET /../etc/passwd → 403 Forbidden
GET /../../secret.txt → 403 Forbidden
GET //etc/hosts → 403 Forbidden

Host Header Validation

All requests must include a valid Host header:

Valid:

Host: localhost:8080
Host: 127.0.0.1:8080
Host: localhost
Host: 127.0.0.1

Invalid (returns 403):

Host: evil.com
Host: attacker.example.com

Missing (returns 400):

No Host header present

Request Size Limits

Maximum request size: 8,192 bytes (8 KB)
Connection queue: 50 connections
Requests per connection: 100 maximum

⚙️ Configuration

Server Parameters

Parameter	Default	Description
`Host`	127.0.0.1	Server bind address
`Port`	8080	Server listening port
`MaxThreads`	10	Worker thread pool size
`ResourcesDir`	resources	Static files directory
`UploadDir`	resources/uploads	JSON upload directory
`KeepAliveMax`	100	Max requests per connection
`KeepAliveTime`	30	Connection timeout (seconds)
`ConnQueueSize`	50	Connection queue size
`MaxRequestSize`	8192	Max request size (bytes)

Modify Configuration

Edit the configuration in pkg/config/config.go or use environment variables:

// Environment variables
export SERVER_PORT=8000
export SERVER_MAX_THREADS=20
export SERVER_KEEP_ALIVE_TIME=60s

// Or modify config.yaml
server:
  port: "8000"
  max_threads: 20
  keep_alive_time: 60s

📊 Performance

Benchmarks

Tested on: Modern multi-core systems with 8GB+ RAM

Metric	Value
Requests per second	2000+
Average response time	<10ms
Concurrent connections	50+
Memory usage	~15MB
CPU usage (10 threads)	~10%

Throughput

Small files (<100KB): ~2000 requests/second
Medium files (1MB): ~100 requests/second
Large files (>10MB): ~20 requests/second

Scalability

Thread pool prevents resource exhaustion
Connection queue handles traffic spikes
Keep-Alive reduces connection overhead
Configurable for different workloads

💡 Examples

Example 1: Serve Custom Content

Place your HTML files in the resources directory:

# Add your file
echo "<h1>My Page</h1>" > resources/mypage.html

# Access it
curl http://localhost:8080/mypage.html

Example 2: Upload JSON Data

// Using JavaScript fetch
fetch('http://localhost:8080/upload', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
        name: 'John Doe',
        email: '[email protected]'
    })
})
.then(res => res.json())
.then(data => console.log(data));

Example 3: Download File Programmatically

# Using Python requests
import requests

response = requests.get('http://localhost:8080/large-banner.png')
with open('downloaded.png', 'wb') as f:
    f.write(response.content)
    
print(f"Downloaded {len(response.content)} bytes")

Example 4: Keep-Alive Connection

# Using curl with keep-alive
curl -v -H "Connection: keep-alive" \
    http://localhost:8080/ \
    http://localhost:8080/about.html

⚠️ Limitations

Known Limitations

File Size: Files are loaded entirely into memory before sending
Chunked Transfer: Not implemented; uses Content-Length only
HTTPS: Only HTTP supported; no TLS/SSL
Multipart Forms: Only JSON POST requests supported
WebSocket: Not supported
HTTP/2: Only HTTP/1.x protocols

Future Enhancements

Streaming implementation for large files
HTTPS/TLS support
WebSocket support
HTTP/2 protocol support
Advanced caching strategies
Load balancing capabilities

🤝 Contributing

Contributions are welcome! Here's how you can help:

Development Setup

# Clone repository
git clone https://github.com/Shreyanshsingh23/http-server.git
cd http-server

# Install Go dependencies
go mod tidy

# Run tests
go test -v ./cmd/server/...

# Build
go build -o server cmd/server/main.go

Code Guidelines

Follow Go conventions and gofmt formatting
Add comments for exported functions
Write tests for new features
Update README for significant changes

Reporting Issues

Open an issue on GitHub with:

Description of the problem
Steps to reproduce
Expected vs actual behavior
Go version and OS

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

MIT License

Copyright (c) 2025 HTTP Server Project

Permission is hereby granted, free of charge, to use, copy, modify, 
merge, publish, distribute, sublicense, and/or sell copies of the 
Software, subject to the following conditions...

🙏 Acknowledgments

Go standard library documentation
HTTP/1.1 RFC 7230-7235 specifications
Network programming best practices
Community feedback and contributions

📞 Contact & Support

GitHub Issues: github.com/Shreyanshsingh23/http-server/issues
Documentation: Available in README.md
API Docs: http://localhost:8080/contact.html (when server is running)

🌟 Star History

If you find this project useful, please consider giving it a ⭐ on GitHub!

Built with ❤️ for learning network programming

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Name		Name	Last commit message	Last commit date
Latest commit History 25 Commits
cmd/server		cmd/server
internal		internal
pkg		pkg
resources		resources
.gitignore		.gitignore
Dockerfile		Dockerfile
LICENSE		LICENSE
Makefile		Makefile
README.md		README.md
docker-compose.yml		docker-compose.yml
go.mod		go.mod
server.exe		server.exe

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