FTP over Implicit TLS (Ssl, AuthSsl, AutoFix)

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Demonstrates the SSL/TLS connection-mode properties Ssl, AuthSsl, and AutoFix. Setting Ssl true selects implicit FTPS, in which TLS begins immediately after the TCP connection on port 990.

Background: FTP has two ways to add TLS: implicit (this example) starts encrypted from the first byte on a dedicated port, 990; explicit (via AuthTls) connects in the clear on port 21 and issues AUTH TLS to upgrade. Explicit is the modern standard; implicit persists mainly for legacy servers. AuthSsl is an obsolete AUTH SSL variant to avoid. AutoFix, on by default, infers the mode from the port — disable it when you set these properties explicitly so it does not override your choice.

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bool success = false;

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

ftp.Hostname = "ftp.example.com";
ftp.Username = "myFtpLogin";

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
ftp.Password = "myPassword";

//  Ssl = true selects IMPLICIT FTPS: TLS begins immediately after the TCP connection, before
//  the greeting.  Port 990 is conventional for implicit FTPS.  Ssl takes priority over AuthTls
//  and AuthSsl.
ftp.Ssl = true;
ftp.Port = 990;

//  AuthSsl selects the legacy AUTH SSL command and is very uncommon -- use AuthTls (explicit
//  FTPS) for modern servers instead.  Left false here.
ftp.AuthSsl = false;

//  AutoFix (default true) automatically adjusts Ssl/AuthTls/AuthSsl based solely on the Port
//  (21 or 990).  Disable it when setting these properties explicitly, as here.
ftp.AutoFix = false;

success = ftp.Connect();
if (success == false) {
    Debug.WriteLine(ftp.LastErrorText);
    return;
}

Debug.WriteLine("Connected using implicit FTPS.");

success = ftp.Disconnect();
if (success == false) {
    Debug.WriteLine(ftp.LastErrorText);
    return;
}