Без подключения к ftp с помощью c#

Я могу создать папку, могу переименовать файл, но не могу загрузить и скачать файл на ftp. Показано исключение System.Net.WebException: удаленный сервер вернул ошибку: (500) Синтаксическая ошибка, команда не распознана.

Кто-нибудь знает, почему?

файл журнала: System.Net Information: 0 : [6112] FtpControlStream#7746814 - Resposta recebida [500 PORT/EPRT (Active Mode/Extended Active Mode) is not supported. Use PASV/EPSV instead of this] System.Net Information: 0 : [6112] FtpWebRequest#30923613::(Liberando a conexão de FTP#7746814.) System.Net Error: 0 : [6112] Exceção em FtpWebRequest#30923613::GetRequestStream - O servidor remoto retornou um erro: (500) Erro de sintaxe, comando não reconhecido.

Код:

 /* Upload File */
public void upload(string remoteFile, string localFile)
{
    try
    {
        /* Create an FTP Request */
        ftpRequest = (FtpWebRequest)FtpWebRequest.Create(host + remoteFile);
        /* Log in to the FTP Server with the User Name and Password Provided */
        ftpRequest.Credentials = new NetworkCredential(user, pass);
        /* When in doubt, use these options */
        ftpRequest.UseBinary = true;
        ftpRequest.UsePassive = false;
        ftpRequest.KeepAlive = true;

        /* Specify the Type of FTP Request */
        ftpRequest.Method = WebRequestMethods.Ftp.UploadFile;
        /* Establish Return Communication with the FTP Server */
        Stream ftpStream = ftpRequest.GetRequestStream();
        /* Open a File Stream to Read the File for Upload */
        FileStream localFileStream = new FileStream(localFile, FileMode.Create);
        /* Buffer for the Downloaded Data */
        byte[] byteBuffer = new byte[bufferSize];
        int bytesSent = localFileStream.Read(byteBuffer, 0, bufferSize);
        /* Upload the File by Sending the Buffered Data Until the Transfer is Complete */
        try
        {
            while (bytesSent != 0)
            {
                ftpStream.Write(byteBuffer, 0, bytesSent);
                bytesSent = localFileStream.Read(byteBuffer, 0, bufferSize);
            }
        }
        catch (Exception ex) { Console.WriteLine(ex.ToString()); }
        /* Resource Cleanup */
        localFileStream.Close();
        ftpStream.Close();
        ftpRequest = null;
    }
    catch (Exception ex) { Console.WriteLine(ex.ToString()); }
    return;
}