HTTP-C: Single-Header HTTP Server Library

A minimal, memory-efficient HTTP/1.0 server library for embedded systems, condensed into a single header file.

Features

• Single Header: Drop http.h into your project and #define HTTP_IMPLEMENTATION in one .c file
• Memory Efficient: Static connection pools, no heap allocation in request loop
• Event-Driven: Single-threaded with select(), suitable for embedded
• Portable: Works on Linux, macOS, Windows, and RTOS (with minor modifications)
• HTTP/1.0: Request line and header parsing, with Keep-Alive support

Quick Start

1. Download http.h
2. Create your main.c:

#define HTTP_IMPLEMENTATION
#include "http.h"

static void request_handler(http_conn_t *conn, http_method_t method, const char *uri) {
    if (strcmp(uri, "/hello") == 0 && method == HTTP_METHOD_GET) {
        http_conn_send_response(conn, 200, "Hello World!");
    } else {
        http_conn_send_response(conn, 404, "Not Found");
    }
}

int main() {
    http_server_t server;
    http_server_init(&server, 8080);
    http_server_set_request_handler(&server, request_handler);
    http_server_run(&server);  // Runs forever
    return 0;
}

3. Compile: gcc main.c -o server
4. Run: ./server
5. Test: curl http://localhost:8080/

Output:

Server listening on 0.0.0.0:8080
Serving from: .
Try: curl http://localhost:8080/

The server now serves files from the SERVE_PATH directory. Place HTML, CSS, JS, and other files in the current directory (or set SERVE_PATH to another directory).

Features

• File Serving: Serves static files with proper MIME types
• Directory Listing: Shows file listings for directories without index.html
• Security: Prevents directory traversal attacks
• URL Decoding: Handles URL-encoded characters
• Embedded Optimized: Uses static memory pools, no dynamic allocation in request path

Configuration

Define these before including http.h to customize:

#define BIND_PORT 8080           // Default server port
#define BIND_IP "0.0.0.0"        // IP address to bind to
#define SERVE_PATH "."           // Root directory for static files
#define MAX_CONNECTIONS 8        // Max concurrent connections
#define READ_BUF_SIZE 4096       // Per-connection read buffer
#define WRITE_BUF_SIZE 4096      // Per-connection write buffer
#define CONNECTION_TIMEOUT_SEC 10 // Idle timeout

API Reference

Server Functions

• int http_server_init(http_server_t *server, int port) - Initialize server
• void http_server_run(http_server_t *server) - Run event loop (blocking)
• void http_server_close(http_server_t *server) - Cleanup
• void http_server_set_request_handler(http_server_t *server, handler) - Set request callback

Connection Functions

• int http_conn_send_response(http_conn_t *conn, int status, const char *body) - Send HTTP response

Types

• http_server_t - Server instance
• http_conn_t - Connection instance
• http_method_t - HTTP methods (GET, POST, etc.)

Memory Usage

• Per Connection: ~5KB (buffers + parser state)
• Total (8 connections): ~40KB + TCP stack
• Binary Size: ~30KB (stripped)

Limitations

• HTTP/1.0 only (no chunked encoding, no HTTP/2)
• No TLS (add mbedTLS separately)
• Single-threaded (use external process manager for multi-core)

License

MIT License - Free for commercial and personal use.