static void ExplicitSSLExample()

{

  try

  {

    FtpClient ftp = new FtpClient();

    //ftp.TraceWriter = Console.Out;



    // Subscribe to the CertificateReceived event

    ftp.CertificateReceived += new CertificateReceivedEventHandler( OnCertificateReceived );



    // Connect to the server normally, unencrypted, at the usual ftp port

    ftp.Connect( "localhost", 21 );



    try

    {

      // Pick an authentication method

      AuthenticationMethod authenticationMethod = AuthenticationMethod.Ssl;



      // Pick verification flags. If unsure, pick 'None'.

      VerificationFlags verificationFlags = VerificationFlags.None;



      // Supply a client certificate to submit to the server. This example doesn't use one

      Certificate clientCertificate = null;



      // Decide if the data channel (for file transfers) will be encrypted or not

      DataChannelProtection dataChannelProtection = DataChannelProtection.Private;



      // Authenticate and encrypt the connection

      ftp.Authenticate( authenticationMethod, verificationFlags, clientCertificate, dataChannelProtection );



      // Login. The exchanged information will be encrypted

      ftp.Login( "username", "password" );



      /* Perform your file transfers */

    }

    finally

    {

      // Make sure we always disconnect

      ftp.Disconnect();



      ftp.CertificateReceived -= new CertificateReceivedEventHandler( OnCertificateReceived );

    }

  }

  catch( Exception exception )

  {

    // Output some information about it

    Console.WriteLine( "-->{0}: {1}\n{2}", exception.GetType().Name, exception.Message, exception.StackTrace );



    // Fetch the inner exception

    exception = exception.InnerException;



    // While there is an exception

    while( exception != null )

    {

      // Output some information about it

      Console.WriteLine( "-->Inner exception: {0}: {1}\n{2}", exception.GetType().Name, exception.Message, exception.StackTrace );



      // Fetch the inner exception

      exception = exception.InnerException;

    }

  }

}



static void OnCertificateReceived( object sender, CertificateReceivedEventArgs e )

{

  // The Status argument property tells you if the server certificate was accepted

  // based on the VerificationFlags provided in the call to Connect().

  if( e.Status != VerificationStatus.ValidCertificate )

  {

    Console.WriteLine( "The server certificate is invalid: {0}", e.Status.ToString() );

    Console.WriteLine( e.ServerCertificate.ToString() );



    // You have three choices here:

    //

    //  1) Refuse the certificate by setting e.Action to VerificationAction.Reject,

    //      thus making the authentication fail. This is e.Action's default value

    //      when the server certificate isn't valid.

    //

    //  2) Set e.Flags to less restrictive criterion and ask the library to

    //      validate the certificate again by setting e.Action to

    //      VerificationAction.VerifyAgain.

    //

    //  3) Force the library to accept this certificate by setting e.Action to

    //      VerificationAction.Accept.

    //

    // We'll do #1 or #3, depending on the user's answer.



    Console.WriteLine( "Do you want to accept this certificate anyway? [Y/N]" );



    int answer = Console.Read();

    if( ( answer == 'y' ) || ( answer == 'Y' ) )

    {

      e.Action = VerificationAction.Accept;

    }

  }

  else

  {

    // e.Action's default value is VerificationAction.Accept

    Console.WriteLine( "Valid certificate received from server." );

  }

}