Read-Only FTP Server

This is a toy implementation of an FTP server built with .NET. It implements most of the FTP specification, but only allows for read operations.

Features

• Full FTP navigation with support for CWD, CDUP, and PWD.
• File listings and metadata via LIST, SIZE, and MDTM.
• File retrieval via RETR with support for binary and ASCII modes.
• Passive mode and extended passive mode support with PASV and EPSV.
• Write operations like STOR, DELE, and MKD are disabled.

Stack

• .NET 10.0 Generic Host with dependency injection.
• Async support for all operations.
• Simple JSON-based configuration for users and server settings.

Getting Started

Local Development

Run the server using the .NET CLI:

dotnet run --project ReadOnlyFTPServer

By default, the server listens on port 2121.

Configuration

The server is configured via three JSON files:

• appsettings.json: Application settings.
• server.json: Port and root path settings.
• users.json: User credentials.

Docker

Build and run using Docker:

docker build -t readonlyftpserver . docker run -p 2121:2121 -p 40000-40100:40000-40100 readonlyftpserver

When running in a container, you must expose both the command port and the range of passive ports. By default, the server uses ports 40000 to 40100 for passive data connections.

Docker Compose

Alternatively, use the provided docker-compose configuration:

services:
  readonlyftpserver:
    build:
      context: .
      dockerfile: ReadOnlyFTPServer/Dockerfile
    ports:
      - "2121:2121"
      - "40000-40100:40000-40100"
    volumes:
      - "/ftp-root:/ftp-root"