An FTP secure client library for C#

private static bool OnCertificateValidation(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
{
    return true;
}

ServicePointManager.ServerCertificateValidationCallback= new RemoteCertificateValidationCallback(OnCertificateValidation);
SslStream _sslStream = new SslStream(new NetworkStream(Csocket), false, new RemoteCertificateValidationCallback( OnCertificateValidation));

///
/// Download a file to the Assembly's local directory,
/// keeping the same file name.
///
///
public void downloadSecure(string remFileName)
{
    downloadSecure(remFileName, "", false);
}

///
/// Download a remote file to the Assembly's local directory,
/// keeping the same file name, and set the resume flag.
///
///
///
public void downloadSecure(string remFileName, Boolean resume)
{
    downloadSecure(remFileName, "", resume);
}

///
/// Download a remote file to a local file name which can include
/// a path. The local file name will be created or overwritten,
/// but the path must exist.
///
///
///
public void downloadSecure(string remFileName, string locFileName)
{
    downloadSecure(remFileName, locFileName, false);
}

///
/// Download a remote file to a local file name which can include
/// a path, and set the resume flag. The local file name will be
/// created or overwritten, but the path must exist.
///
///
///
///
public void downloadSecure(string remFileName, string locFileName, Boolean resume)
{
    if (!logined)
    {
        login();
    }

    setBinaryMode(true);

    sendCommand("PBSZ 0");
    sendCommand("PROT P");
    sendCommand("PASV");

    if (retValue != 227)
    {
        throw new IOException(reply.Substring(4));
    }

    Console.WriteLine("Downloading file " + remFileName + " from " + remoteHost + "/" + remotePath);

    if (locFileName.Equals(""))
    {
        locFileName = remFileName;
    }

    if (!File.Exists(locFileName))
    {
        Stream st = File.Create(locFileName);
        st.Close();
    }

    FileStream output;
    if (resume)
    {
        output = new FileStream(locFileName, FileMode.Open);
    }
    else
    {
        output = new FileStream(locFileName, FileMode.Truncate);
    }

    Socket cSocket = createDataSocket();
    isUpload = false;
    this.getSslDataStream(cSocket);

    long offset = 0;

    if (resume)
    {

        offset = output.Length;

        if (offset > 0)
        {
            sendCommand("REST " + offset);
            if (retValue != 350)
            {
                //throw new IOException(reply.Substring(4));
                //Some servers may not support resuming.
                offset = 0;
            }
        }

        if (offset > 0)
        {
            if (debug)
            {
                Console.WriteLine("seeking to " + offset);
            }
            long npos = output.Seek(offset, SeekOrigin.Begin);
            Console.WriteLine("new pos=" + npos);
        }
    }

    sendCommand("RETR " + remFileName);
    stream2.AuthenticateAsClient(
        remoteHost,
        null,
        System.Security.Authentication.SslProtocols.Ssl3 |
        System.Security.Authentication.SslProtocols.Tls,
        true);

    if (stream2.IsAuthenticated)
    {
        if (!(retValue == 125 || retValue == 150))
        {
            throw new IOException(reply.Substring(4));
        }

        while (true)
        {

            bytes = stream2.Read(buffer, 0, buffer.Length);
            output.Write(buffer, 0, bytes);

            if (bytes <= 0)
            {
                break;
            }
        }
        output.Close();
    }
    if (cSocket.Connected)
    {
        cSocket.Close();
    }

    Console.WriteLine("");

    readReply();

    if (!(retValue == 226 || retValue == 250))
    {
        throw new IOException(reply.Substring(4));
    }

}

this.getSslDataStream(cSocket);

string cmd = "AUTH SSL";
ftp.sendCommand(cmd);

//Create  SSL Stream
ftp.getSslStream();
ftp.setUseStream(true);

private SslStream stream2;

public void getSslDataStream(Socket Csocket) {
   SslStream _sslStream = new SslStream(new NetworkStream(Csocket));
   stream2 = _sslStream;
}

public void uploadSecure(string fileName, Boolean resume) {
  ....
  Socket cSocket = createDataSocket();
  isUpload = true;
  this.getSslDataStream(cSocket);

  ....
  sendCommand("STOR " + Path.GetFileName(fileName)) // fileName is the relative file
  stream2.AuthenticateAsClient(remoteHost,
      null,
      System.Security.Authentication.SslProtocols.Ssl3 |
      System.Security.Authentication.SslProtocols.Tls,
      true);
  if (stream2.IsAuthenticated) {
     if (!(retValue == 125 || retValue == 150)) {
        throw new IOException(reply.Substring(4));
     }
     .....
     this.stream2.Close();
  }
  if (cSocket.Connected)
  {
     cSocket.Close();
  }
  readReply();
  ......
  }
}