(.NET Core C#) Verify FTP SSL Server Certificate

This example demonstrates how to verify the FTP server's certificate and authenticity. The intent is to verify the authenticity of the server before passing a login/password to it.

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Ftp2 ftp = new Chilkat.Ftp2();

ftp.Hostname = "ftp.myftpserver.com";
ftp.Username = "myUsername";
ftp.Password = "myPassword";

// Establish an AUTH SSL secure channel after connection
// on the standard FTP port 21.
ftp.AuthSsl = true;

// The Ssl property is for establishing an implicit SSL connection
// on port 990.  Do not set it.
ftp.Ssl = false;

// Indicate that the FTP server must have a verifiable SSL certificate.
// Do not accept self-signed certs or certificates that are
// expired, revoked, or cannot be verified to a root authority:
ftp.RequireSslCertVerify = true;

// You may also set a requirement.  In this example,
// the certificate's Common Name (CN) must match the
// required string exactly:
ftp.SetSslCertRequirement("subjectcn","Chilkat Software, Inc.");

// Connect and login to the FTP server.
bool success = ftp.Connect();
if (success != true) {
    Debug.WriteLine(ftp.LastErrorText);
    return;
}
else {
    // LastErrorText contains information even when
    // successful. This allows you to visually verify
    // that the secure connection actually occurred.
    Debug.WriteLine(ftp.LastErrorText);
}

// After logging on, you may examine the FTP server's cert:
Chilkat.Cert cert = null;
cert = ftp.GetSslServerCert();
if (ftp.LastMethodSuccess != true) {
    Debug.WriteLine("No server certificate!");
}
else {
    // Display the distinguished name of the SSL cert.
    Debug.WriteLine(cert.SubjectDN);
}

Debug.WriteLine("Secure FTP Channel Established!");

// Do whatever you're doing to do ...
// upload files, download files, etc...

success = ftp.Disconnect();