(Objective-C) FTP through SSH Tunnel with Dynamic Port Forwarding

Demonstrates how to start a background thread that runs a portable SSH tunnel w/ dynamic port forwarding that the foreground thread can be used for establishing FTP sessions through an SSH tunnel.

Note: Some developers may be accustomed to starting an stunnel.exe proxy from https://www.stunnel.org. The stunnel.exe is not necessary here. Chilkat's background thread fulfills the task of what the external stunnel.exe does. Therefore, your application is self-contained, meaning that it can run anywhere because the SSH tunnel proxy is built-in.

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#import <CkoGlobal.h>
#import <CkoSshTunnel.h>
#import <NSString.h>
#import <CkoFtp2.h>

// Starting in v9.5.0.49, all Chilkat classes can be unlocked at once at the beginning of a program
// by calling UnlockBundle.  It requires a Bundle unlock code.
CkoGlobal *chilkatGlob = [[CkoGlobal alloc] init];
BOOL success = [chilkatGlob UnlockBundle: @"Anything for 30-day trial."];
if (success != YES) {
    NSLog(@"%@",chilkatGlob.LastErrorText);
    return;
}

// This example requires Chilkat version 9.5.0.50 or greater.
CkoSshTunnel *tunnel = [[CkoSshTunnel alloc] init];

NSString *sshHostname = @"sftp.example.com";
int sshPort = 22;

// Connect to an SSH server and establish the SSH tunnel:
success = [tunnel Connect: sshHostname port: [NSNumber numberWithInt: sshPort]];
if (success != YES) {
    NSLog(@"%@",tunnel.LastErrorText);
    return;
}

// Authenticate with the SSH server via a login/password
// or with a public key.  
// This example demonstrates SSH password authentication.
success = [tunnel AuthenticatePw: @"mySshLogin" password: @"mySshPassword"];
if (success != YES) {
    NSLog(@"%@",tunnel.LastErrorText);
    return;
}

// Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
// with dynamic port forwarding:
tunnel.DynamicPortForwarding = YES;

// We may optionally require that connecting clients authenticate with our SOCKS proxy server.
// To do this, set an inbound username/password.  Any connecting clients would be required to 
// use SOCKS5 with the correct username/password.
// If no inbound username/password is set, then our SOCKS proxy server will accept both
// SOCKS4 and SOCKS5 unauthenticated connections.

tunnel.InboundSocksUsername = @"chilkat123";
tunnel.InboundSocksPassword = @"password123";

// Start the listen/accept thread to begin accepting SOCKS proxy client connections.
// Listen on port 1080.
success = [tunnel BeginAccepting: [NSNumber numberWithInt: 1080]];
if (success != YES) {
    NSLog(@"%@",tunnel.LastErrorText);
    return;
}

// Now that a background thread is running a SOCKS proxy server that forwards connections
// through an SSH tunnel, it is possible to use any Chilkat implemented protocol that is SOCKS capable,
// such as HTTP, POP3, SMTP, IMAP, FTP, etc.  The protocol may use SSL/TLS because the SSL/TLS
// will be passed through the SSH tunnel to the end-destination.  Also, any number of simultaneous
// connections may be routed through the SSH tunnel.

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

// Indicate that the HTTP object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
ftp.SocksHostname = @"localhost";
// The SocksPort must equal the port passed to BeginAccepting above.
ftp.SocksPort = [NSNumber numberWithInt:1080];
ftp.SocksVersion = [NSNumber numberWithInt:5];
// The SOCKS5 login/password set here must equal the InboundSocksUsername/Password set above.
ftp.SocksUsername = @"chilkat123";
ftp.SocksPassword = @"password123";

// This is the actual FTP server domain or IP address, and the login/password for the user account on the destination FTP server.
ftp.Hostname = @"ftp.someFtpServer.com";
ftp.Username = @"myLogin";
ftp.Password = @"myPassword";
ftp.AuthTls = YES;

// Connect and login (via the SSH tunnel) to the FTP server.
success = [ftp Connect];
if (success != YES) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

// Change to the remote directory where the file is located.
// This step is only necessary if the file is not in the root directory
// for the FTP account.
success = [ftp ChangeRemoteDir: @"junk"];
if (success != YES) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

NSString *localFilename = @"c:/temp/hamlet.xml";
NSString *remoteFilename = @"hamlet.xml";

// Download a file.  (the data connection is also automatically established through the 
// SSH tunnel using dynamic port forwarding..)
success = [ftp GetFile: remoteFilename localPath: localFilename];
if (success != YES) {
    NSLog(@"%@",ftp.LastErrorText);
    return;
}

// The disconnect is disconnecting with the FTP server and closes the SSH tunnel.
// The background tunnel thread is still running, and may be used for subsequent FTP connections,
// or even connections for any other purpose, such as HTTP, IMAP, SMTP, POP3, etc.
success = [ftp Disconnect];

// When the app is finished with the tunnel, it can cleanup..

// Stop the background listen/accept thread:
BOOL waitForThreadExit = YES;
success = [tunnel StopAccepting: waitForThreadExit];
if (success != YES) {
    NSLog(@"%@",tunnel.LastErrorText);
    return;
}

// Close the SSH tunnel (would also kick any remaining connected clients).
success = [tunnel CloseTunnel: waitForThreadExit];
if (success != YES) {
    NSLog(@"%@",tunnel.LastErrorText);
    return;
}