This project has been created as part of the 42 curriculum by rhiguita, migugar2, almejia-

Webserv — Non-Blocking HTTP/1.1 Web Server in C++98

Description

Webserv is an asynchronous, event-driven HTTP/1.1 web server implemented in C++98. Inspired by NGINX, it provides a high-performance network service handling multiple concurrent connections using a single-threaded Linux epoll event loop without blocking I/O calls.

flowchart TD
    subgraph Network["Network & Kernel Layer"]
        A["Listening Sockets"] -->|accept| E["EpollManager (epoll_wait)"]
        C["Client Connections"] <-->|non-blocking read / write| E
        P["CGI Pipes"] <-->|non-blocking IPC| E
    end

    subgraph Core["Event Dispatcher"]
        E -->|New Connection| SH["ServerHandler"]
        E -->|Client Event| CH["ClientHandler"]
        E -->|Pipe Event| CGI_H["CgiReadHandler / CgiWriteHandler"]
    end

    subgraph Pipeline["HTTP Processing Pipeline"]
        CH --> HP["HttpParser (FSM Parser)"]
        HP --> R["Router & Virtual Host Matching"]
        R -->|Static GET| GE["GetExecutor"]
        R -->|Upload / POST| PE["PostExecutor"]
        R -->|File DELETE| DE["DeleteExecutor"]
        R -->|CGI Gateway| CE["CgiExecutor (fork & execve)"]
    end

    subgraph State["State & Sessions"]
        R <--> SM["SessionManager (In-Memory Cookies)"]
    end

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Core Architecture & Features

• Single-Threaded Asynchronous Event Loop (EpollManager):

  • Centralized multiplexer using Linux epoll with EPOLLIN, EPOLLOUT, and EPOLLRDHUP.
  • Non-blocking I/O across listening sockets, client TCP sockets, and asynchronous CGI unidirectional pipes.
  • Strict single-read/single-write call discipline per event dispatch.
  • Automatic connection idle timeout sweeps (60-second inactivity detection).

• Robust HTTP/1.1 & HTTP/1.0 Parser (HttpParser):

  • Incremental Finite State Machine (FSM) reading raw byte streams without payload corruption.
  • Full support for Transfer-Encoding: chunked (dynamic de-chunking) and Content-Length identity encoding.
  • HTTP/1.1 mandatory Host header validation and HTTP/1.0 backward compatibility (Connection: close default).
  • Pipelining and persistent Keep-Alive connections with preserved buffer state.

• Routing & Virtual Hosts (Router, GetExecutor, PostExecutor, DeleteExecutor):

  • Multi-port listening and virtual host resolution via Host header and server_name.
  • Standard HTTP methods:
    • GET: Static file serving, custom MIME type resolution, automatic directory indexing (autoindex on/off), and default index resolution.
    • POST: Raw binary uploads and multipart/form-data parsing when upload_enable on is configured; standard payload handling.
    • DELETE: File removal with permission validation and directory protection.
  • HTTP Redirections (302 Found).
  • Configurable client_max_body_size per server and per location route (413 Payload Too Large).
  • Customizable error pages with fallback HTML generation.

• Asynchronous CGI Subsystem (CgiExecutor, CgiReadHandler, CgiWriteHandler):

  • Execution of CGI scripts (e.g. Python, Shell, compiled binaries) based on configured file extensions.
  • Compliance with RFC 3875: standard environment variables (REQUEST_METHOD, SCRIPT_FILENAME, PATH_INFO, QUERY_STRING, SERVER_PROTOCOL, HTTP_*).
  • Working directory (chdir) isolation to the script parent directory.
  • Concurrent non-blocking pipe writing (request body feeding) and reading (response streaming) without deadlocks or buffer truncation.

• Bonus Modules:

  • Session & Cookie Manager (SessionManager): In-memory session store generating 32-character secure alphanumeric tokens (session_id) with visit counting, client IP tracking, automatic expiration sweeps, and HTTP Set-Cookie integration.
  • Multi-CGI Support: Independent handler mappings per file extension.

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Instructions

Compilation

Build the executable using GNU Make with strict flags (-Wall -Wextra -Werror -std=c++98 -pedantic):

make        # Compiles the webserv binary
make clean  # Removes object and dependency files
make fclean # Removes objects and webserv executable
make re     # Recompiles from scratch

Execution

Run the server by passing a configuration file path (or omit to use config/default.conf):

./webserv [path/to/configuration.conf]

Example:

./webserv config/default.conf

To run with the 42 official test suite configuration:

./webserv config/tester.conf

Configuration File Syntax

Configuration files follow an NGINX-style block hierarchy:

server {
    listen 8080;
    server_name localhost;
    root ./www;
    client_max_body_size 10m;

    error_page 404 /errors/404.html;
    error_page 500 502 /errors/50x.html;

    location / {
        methods GET;
        index index.html;
        autoindex off;
    }

    location /upload {
        methods GET POST DELETE;
        upload_enable on;
        upload_store ./www/uploads;
    }

    location /cgi-bin {
        root ./www/cgi-bin;
        methods GET POST;
        cgi .py /usr/bin/python3;
        cgi .sh /bin/sh;
    }

    location /old {
        redirect /;
    }
}

Verification & Testing

1. Static Content & Custom Error Pages:

   curl -i http://localhost:8080/
   curl -i http://localhost:8080/nonexistent

2. File Upload & Deletion:

   # Upload a file
   curl -i -X POST http://localhost:8080/upload/data.txt -d "Sample text"
   
   # Retrieve uploaded file
   curl -i http://localhost:8080/upload/data.txt
   
   # Delete file
   curl -i -X DELETE http://localhost:8080/upload/data.txt

3. CGI Execution:

   curl -i http://localhost:8080/cgi-bin/hello.py

4. Official 42 Tester Suite:

   ./tester/tester http://localhost:8000

5. Memory Leak Verification (Valgrind):

   valgrind --leak-check=full --show-leak-kinds=all --track-origins=yes ./webserv config/default.conf

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Resources

Documentation & Standards

• RFC 2616 — Hypertext Transfer Protocol -- HTTP/1.1
• RFC 3875 — The Common Gateway Interface (CGI) Version 1.1
• Linux Programmer's Manual: epoll(7)
• Linux Programmer's Manual: fcntl(2)
• Linux Programmer's Manual: socket(2)

AI Usage Disclosure

In accordance with Chapter III ("AI Instructions") of the 42 Common Core curriculum:

• AI Tool: Antigravity / Gemini DeepMind AI Coding Assistant.
• Scope of AI Assistance: Assisted with system architecture auditing, reproducing subtle non-blocking pipe edge-cases (Linux EPOLLHUP/EAGAIN nuances during high-volume transfers), identifying memory move bottlenecks in large response serialization, and reviewing POSIX/C++98 conformance.
• Verification & Ownership: All logic, concurrency flows, and data structures were audited, understood, and validated using Valgrind, custom test requests, and the 42 official tester suite.