Simple HTTP Server in C

A lightweight, multithreaded HTTP/1.1 server written in pure C with threads. For learning some network.

Features

Multithreaded - Handles concurrent connections using pthreads
Directory serving - Serve entire directory trees
Single file mode - Serve a specific file
logs - Request logs in standard format
Security - Path traversal protection
MIME type detection - Auto-detects content types (HTML, CSS, JS, images, etc.)

Quick Start

Compilation

gcc -pthread src/main.c src/netlib.c -I src -o server

Usage Examples

Serve a directory:

./server -d ./public

Serve a single file:

./server -f index.html

Custom port with logging:

./server -d ./website -p 8080 -l access.log

Display help:

./server -h

Command-Line Options

Option	Description	Default
-d <directory>	Serve files from directory	Current directory
-f <file>	Serve single file to all requests	-
-p <port>	Port number	4221
-l <logfile>	Log file path	stdout only
-h	Display help message	-

URL Structure

Directory Mode (-d)

• http://localhost:4221/ → serves index.html
• http://localhost:4221/style.css → serves style.css
• http://localhost:4221/js/app.js → serves js/app.js
• http://localhost:4221/images/logo.png → serves images/logo.png

Single File Mode (-f)

./server -f mypage.html

• Must access: http://localhost:4221/mypage.html
• Will 404: http://localhost:4221/

Log Format

The server logs requests in Apache Common Log Format:

127.0.0.1 - - [10/Nov/2025:14:32:20 +0100] "GET /index.html HTTP/1.1" 200 1234

Performance & Benchmarking

This section summarizes the results of a wrk benchmark used to evaluate the server's concurrency handling and throughput.

Test environment

• Tool: wrk
• Concurrency: 3,000 simultaneous connections
• Threads: 12
• Duration: 30 seconds

Example command used:

w rk -t12 -c3000 -d30s http://your-server.example/

(Replace http://your-server.example/ with the endpoint you tested.)

Benchmark results

Metric	Result
Throughput	20,101.81 Requests/sec
Transfer Rate	243.45 MB/sec
Avg Latency	34.84 ms
Total Requests	603,950

Notes & reproducibility

• Run the same wrk command above to reproduce tests.
• Ensure the test environment (network, server CPU, background load) is stable for consistent results.
• For higher-confidence results, run multiple iterations and report averages and standard deviations.

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Project Structure

.
├── src/
│   ├── main.c          # Server initialization and main loop
│   ├── netlib.c        # HTTP handling and file serving
│   └── netlib.h        # Header file with declarations
├── server              # Compiled binary
└── README.md

Security Features

• Path traversal protection (.. blocked)
• Input validation

Technical Details

• Protocol: HTTP/1.1
• Concurrency: One thread per connection (pthread)
• Socket: TCP (AF_INET, SOCK_STREAM)
• Buffer Size: 4KB request buffer
• Response: Supports Content-Type and Content-Length headers

Testing

Start the server:

./server -d . -l server.log

Test with curl:

curl http://localhost:4221/README.md
curl -I http://localhost:4221/README.md  # Headers only

Test with browser (port 4221 is the default):

http://localhost:4221/

Limitations

• Only GET method supported
• No HTTPS/TLS support
• No compression (gzip)
• No keep-alive connections
• No caching headers

License

MIT License - Feel free to use and modify!

Author

Built as a learning project to understand HTTP servers and network programming in C.

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