Webbol

A minimal static web server written in COBOL using GnuCOBOL.

Features

• Serves static files from the current directory
• Automatic MIME type detection for common file types
• HTTP status codes: 200 (OK), 403 (Forbidden), 404 (Not Found)
• Path traversal attack prevention
• Clean request logging with full HTTP headers
• Defaults to index.html for root path requests

Requirements

• GnuCOBOL (cobc) compiler
• POSIX-compatible operating system (Linux, macOS, BSD)
• make

Installing GnuCOBOL

macOS:

Ubuntu/Debian:

sudo apt-get install gnucobol

Fedora/RHEL:

sudo dnf install gnucobol

Building

Clone or download the repository, then compile:

This will compile all modules and create the webserver executable.

To clean build artifacts:

Usage

Start the server from the directory you want to serve:

The server will start on port 8080 and serve files from the current directory.

Example

# Create a test HTML file
echo "
Hello from COBOL!
" > index.html

# Start the server
./webserver

# In another terminal, test it
curl http://localhost:8080/

Accessing the Server

Once running, you can access files via:

• http://localhost:8080/ – serves index.html from the current directory
• http://localhost:8080/filename.html – serves the specified file
• http://localhost:8080/path/to/file.txt – serves files from subdirectories

Press Ctrl+C to stop the server.

Configuration

To change the server port, edit config.cpy and modify the SERVER-PORT value:

01 SERVER-PORT          PIC 9(5) VALUE 8080.

Then recompile with make.

Project Structure

webbol/
├── Makefile              # Build configuration
├── README.md            # This file
├── config.cpy           # Server configuration
├── socket-defs.cpy      # Socket structure definitions
├── http-structs.cpy     # HTTP data structures
├── file-structs.cpy     # File handling structures
├── path-utils.cbl       # Path validation and sanitization
├── mime-types.cbl       # MIME type detection
├── file-ops.cbl         # File reading operations
├── http-handler.cbl     # HTTP request/response handling
└── webserver.cbl        # Main server program

Supported MIME Types

• HTML: text/html
• CSS: text/css
• JavaScript: application/javascript
• JSON: application/json
• XML: application/xml
• Plain text: text/plain
• PNG: image/png
• JPEG: image/jpeg
• GIF: image/gif
• SVG: image/svg+xml
• ICO: image/x-icon
• PDF: application/pdf

Additional MIME types can be added by editing mime-types.cbl.

Security Features

• Path traversal prevention: Blocks requests containing .. sequences
• Directory access restriction: Only serves files from the current directory and subdirectories
• Safe file handling: Validates all paths before file system access

Limitations

• Single-threaded: Handles one request at a time
• No SSL/TLS support
• Maximum file size: 64KB
• Line sequential file organization only (text files)
• No caching or compression
• No range requests or partial content support

Troubleshooting

Port already in use:

Bind failed - check if port is in use

Another process is using port 8080. Either stop that process or change the port in config.cpy.

Permission denied:
Ensure the files you’re trying to serve have read permissions and the current user can access them.

File not found (404):
Verify the file exists in the current directory where the server is running. File paths are case-sensitive.

License

This project is released into the public domain. Use it however you’d like.

Acknowledgments

Built with GnuCOBOL, demonstrating that COBOL can still be used for modern systems programming tasks.