(Objective-C) 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 <CkoFtp2.h>
#import <CkoCert.h>

// This example assumes Chilkat Ftp2 to have been previously unlocked.
// See Unlock Ftp2 for sample code.

CkoFtp2 *ftp = [[CkoFtp2 alloc] init];

ftp.Hostname = @"www.authtls-ftps-server.com";
ftp.Username = @"FTP_LOGIN";
ftp.Password = @"FTP_PASSWORD";
ftp.AuthTls = YES;
ftp.Port = [NSNumber numberWithInt:21];

// Connect to the FTP server using explicit TLS (AUTH TLS).
BOOL success = [ftp ConnectOnly];
if (success != YES) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

// Get the FTP server's certificate.
CkoCert *serverCert = [ftp GetSslServerCert];
if (ftp.LastMethodSuccess != YES) {
    NSLog(@"%@",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 != YES) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

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

[ftp Disconnect];
NSLog(@"%@",@"Success.");