Getting Hostname from Client-Connection

[Bizarrus]

If the Server is listen to any address like ftp://0.0.0.0:21, how i can find the connection hostname/domain?

Users have their own subdomain like <user>.example.com and will use these for the FTP-Connection.
But the connection parameter on the login-Event has no informations about that.

The FtpConnection object has only following informations:

FtpConnection {
    server: FtpServer {
        options: {
          url: 'ftp://0.0.0.0:21',
          // [...]
        },
        url: Url {
          host: '0.0.0.0:21',
          port: '21',
          hostname: '0.0.0.0',
          href: 'ftp://0.0.0.0:21/',
          // [...]
        },
        server: Server {
          _connectionKey: '4:0.0.0.0:21',
          // [...]
        },
    },
    commandSocket: <ref *2> Socket {
        _sockname: { address: '89.22.***.***', family: 'IPv4', port: 21 }, // The Server-IP
        _peername: { address: '95.223.***.***', family: 'IPv4', port: 26743 }, // The Client-IP
        // [...]
    },
    log: Logger {
        src: false,
        fields: {
            hostname: 'example.com', // No subdomain!
            ip: '95.223.***.***', // The Client-IP
            // [...]
        },
}