HTTPlite

The goal is to build a functional HTTP/1.1 server from scratch to understand the fundamentals of the protocol and low-level network programming using TCP sockets in C++.

Features Implemented (So Far)

• TCP Server Setup: Binds to a port (4221) and listens for incoming TCP connections. Uses SO_REUSEADDR for quick restarts during development.
• HTTP Request Parsing:
  • Parses the request line to extract the HTTP method (GET, POST) and the request target (path).
  • Reads and parses HTTP headers into a case-insensitive map (key-value pairs). Handles the end-of-headers marker (\r\n\r\n).
  • Reads the HTTP request body based on the Content-Length header, necessary for POST requests.
• HTTP Response Generation:
  • Constructs valid HTTP/1.1 responses with status line, headers, and body.
  • Supports status codes: 200 OK, 201 Created, 400 Bad Request, 404 Not Found, 500 Internal Server Error.
• Routing: Handles requests based on the path and method:
  • GET /: Responds with 200 OK.
  • GET /echo/{string}: Responds with 200 OK and echoes {string} in the body with Content-Type: text/plain.
  • GET /user-agent: Responds with 200 OK and the value of the User-Agent request header in the body.
  • GET /files/{filename}: Responds with 200 OK, Content-Type: application/octet-stream, and the file content if the file exists in the specified directory. Responds with 404 Not Found otherwise. Includes basic path traversal prevention.
  • POST /files/{filename}: Reads the request body and writes it to a file named {filename} in the specified directory. Responds with 201 Created on success. Includes basic path traversal prevention.
• Concurrency: Handles multiple client connections concurrently using C++ std::thread (thread-per-connection model). The main thread accepts connections and launches detached worker threads to handle each client independently.
• File System Interaction:
  • Reads files from a specified directory (passed via --directory command-line argument) for GET /files/... requests.
  • Writes files to the specified directory for POST /files/... requests.
• Modularity: Code is structured into server.cpp (main server loop, threading) and request_handler.h/.cpp (request reading, parsing, routing, response generation).

Technologies Used

• Language: C++ (using C++17/C++23 features like std::thread, std::string, std::unordered_map, etc.)
• Build System: CMake
• Core Libraries:
  • Standard C++ Library (<iostream>, <string>, <vector>, <sstream>, <fstream>, <unordered_map>, <thread>, <algorithm>, <cctype>)
  • POSIX Sockets API (<sys/socket.h>, <netdb.h>, <arpa/inet.h>, <unistd.h>) for low-level networking.
  • Zlib (Linked via CMake for potential future compression stage).