## Open-source free C# FTPS Server .Net 10 Library without dependencies

A FTPS (FTP over TLS) server implementation in C# with logging, user permissions, and flexible configuration options. Aimed for Windows, Linux, Android and macOS, and for embedding in other .NET apps.

For Android see File System implementation and sample code at repository (Avalonia based).

Does not have dependencies.

Uses permissive license CC0-1.0.

This is a sample implementation provided for:
- ✅ Learning and education
- ✅ Internal corporate use
- ✅ Personal projects
- ✅ Modification and customization

Not recommended for:
- ⚠️ Internet-facing production without security review
- ⚠️ Mission-critical systems without testing
- ⚠️ Compliance-required environments without audit

## Features

- ✅ **User Permissions** - Granular control over Read/Write operations
- ✅ **Per-User Root Folders** - Isolated directories for each user
- ✅ **TLS/SSL Encryption** - Secure FTPS connections
- ✅ **Full FTP Protocol** - All standard FTP commands supported
- ✅ **Path Security** - Protection against directory traversal attacks

## ⚙️ Configuration

See 
- https://github.com/drweb86/dotnet-ftps-server/blob/main/sources/FtpsServerLibrary/FtpsServerSettings.cs and 
- https://github.com/drweb86/dotnet-ftps-server/blob/main/sources/FtpsServerLibrary/FtpsServerUserAccount.cs .


| Parameter                               | Required  | Default value | Remarks                                                                                                                 |
|-----------------------------------------|-----------|---------------|-------------------------------------------------------------------------------------------------------------------------|
| ServerSettings.Ip                       | No        | 0.0.0.0       | The IP address the server listens on. 0.0.0.0, ::, and ::0 listen on every IPv4 and IPv6 interface. A specific address listens on that address only. |
| ServerSettings.Port                     | No        | 2121          | The Port for server to listen to.                                                                                       |
| ServerSettings.MaxConnections           | No        | 10            | Maximum number of simultaneous server connections.                                                                      |
| ServerSettings.CertificatePath          | No        |               | PEM, DER or PKCS#12 PFX file. PFX file is opened with CertificatePassword (if specified).                               |
| ServerSettings.CertificatePassword      | No        |               | Certificate password. When specified, will be used for opening certificate from CertificatePath.                        |
| ServerSettings.CertificateStoreName     | No        |               | Certificate store name. Possible values: AuthRoot, CertificateAuthority, My, Root, TrustedPublisher. Used when CertificateStoreName, CertificateStoreLocation and CertificateStoreSubject are together specified. |
| ServerSettings.CertificateStoreLocation | No        |               | Certificate store location. Possible values: CurrentUser, LocalMachine. Used when CertificateStoreName, CertificateStoreLocation and CertificateStoreSubject are together specified.                              |
| ServerSettings.CertificateStoreSubject  | No        |               | Certificate store subject by which certificate will be searched in certificate store and location. Used when CertificateStoreName, CertificateStoreLocation and CertificateStoreSubject are together specified.   |
| Users[].Login                           | Yes       |               | User's login.                                                                   |
| Users[].Password                        | Yes       |               | User's password.                                                                |
| Users[].Folder                          | Yes       |               | User's folder.                                                                   |
| Users[].Read                            | Yes       |               | Can user read folder contents and download files.                               |
| Users[].Write                           | Yes       |               | Can user create, upload, write, delete, rename operations on files and folders. |

If certificate is not specified, self-signed certificate will be created and stored in %localappdata%\FtpsServerLibrary\Certificates. On Windows and Linux its password is random and stored beside the file with an OS-backed key (DPAPI for the current user, or a key derived from the Linux machine id). A certificate saved by an older version with the password `test` is rewritten with that key the next time the server starts. Android and macOS keep the password `test`.

## 🚀 Run

```
using FtpsServerLibrary;

var config = new FtpsServerConfiguration
{
    ServerSettings = new FtpsServerSettings { },
    Users = [
        new FtpsServerUserAccount { Folder = @"c:\folder", Login = "admin", Password = "admin", Read = true, Write = true}
    ]
};
var server = new FtpsServer(new StubLog(), config, new FtpsServerFileSystemProvider());
await server.StartAsync();
Console.WriteLine("Server is started at 0.0.0.0 listening on port 2121 with self-signed certificate");
Console.ReadLine();
server.Stop();

class StubLog : IFtpsServerLog
{
    public void Debug(string message) { }
    public void Error(Exception ex, string message) { }
    public void Fatal(Exception ex, string message) { }
    public void Info(string message) { }
    public void Warn(string message) { }
}
```

If you want support of Linux file system, it's available via Android File System provider, see source code of project. Its implemented for Avalonia backend.