(Java) FTP Connect, Examine Server Certificate, and then Authenticate

Demonstrates how to connect to an FTP server, examine the server's SSL/TLS certificate, and then, if it meets the application's security requirements, proceed to authenticate.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example assumes Chilkat Ftp2 to have been previously unlocked.
    // See Unlock Ftp2 for sample code.

    CkFtp2 ftp = new CkFtp2();

    ftp.put_Hostname("www.authtls-ftps-server.com");
    ftp.put_Username("FTP_LOGIN");
    ftp.put_Password("FTP_PASSWORD");
    ftp.put_AuthTls(true);
    ftp.put_Port(21);

    // Connect to the FTP server using explicit TLS (AUTH TLS).
    boolean success = ftp.ConnectOnly();
    if (success != true) {
        System.out.println(ftp.lastErrorText());
        return;
        }

    // Get the FTP server's certificate.
    CkCert serverCert = ftp.GetSslServerCert();
    if (ftp.get_LastMethodSuccess() != true) {
        System.out.println(ftp.lastErrorText());
        return;
        }

    // Now that we have the certificate, we can check it in any way we desire.
    // (See the online reference documentation for the certificate object's methods
    // and properties)...

    // Assuming the certificate is OK, proceed to authenticate with the FTP server.
    success = ftp.LoginAfterConnectOnly();
    if (success != true) {
        System.out.println(ftp.lastErrorText());
        return;
        }

    // 
    // Proceed with uploading/download files, etc...
    // 

    ftp.Disconnect();
    System.out.println("Success.");
  }
}