(Objective-C) SMTP over Multiple Hop SSH

Demonstrates how to send email (using TCP or TLS) tunneled through mulitple-hop SSH. The scheme looks like this:

Application => ServerSSH1 => ServerSSH2 => SmtpServer

The ConnectThroughSsh and UseSsh methods are added in Chilkat version 9.5.0.55 to accomplish this task.

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#import <CkoSsh.h>
#import <CkoMailMan.h>
#import <CkoEmail.h>

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

CkoSsh *ssh1 = [[CkoSsh alloc] init];

// Connect directly to the 1st SSH server.
BOOL success = [ssh1 Connect: @"serverssh1.com" port: [NSNumber numberWithInt: 22]];
if (success != YES) {
    NSLog(@"%@",ssh1.LastErrorText);
    return;
}

// Authenticate using login/password:
success = [ssh1 AuthenticatePw: @"ssh1Login" password: @"ssh1Password"];
if (success != YES) {
    NSLog(@"%@",ssh1.LastErrorText);
    return;
}

// Connect through the 1st SSH connection to reach a 2nd SSH server.
// Note: Any number of SSH connections may be simultaneously tunneled through a single
// existing SSH connection.
CkoSsh *ssh2 = [[CkoSsh alloc] init];
success = [ssh2 ConnectThroughSsh: ssh1 hostname: @"serverssh2.com" port: [NSNumber numberWithInt: 22]];
if (success != YES) {
    NSLog(@"%@",ssh2.LastErrorText);
    return;
}

// Authenticate with ssh2...
success = [ssh2 AuthenticatePw: @"ssh2Login" password: @"ssh2Password"];
if (success != YES) {
    NSLog(@"%@",ssh2.LastErrorText);
    return;
}

CkoMailMan *mailman = [[CkoMailMan alloc] init];

// Tell the mailman object to connect to the SMTP server though the ssh2 tunnel (which itself is routed through ssh1).
// The connection looks like this:  Application => ServerSSH1 => ServerSSH2 => SMTPServer
success = [mailman UseSsh: ssh2];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// Set the SMTP server.
mailman.SmtpHost = @"smtp.someserver.com";

// Set the SMTP login/password (if required)
mailman.SmtpUsername = @"myUsername";
mailman.SmtpPassword = @"myPassword";

// Create a new email object
CkoEmail *email = [[CkoEmail alloc] init];

email.Subject = @"This is a test";
email.Body = @"This is a test";
email.From = @"Chilkat Support <support@chilkatsoft.com>";
success = [email AddTo: @"Chilkat Admin" emailAddress: @"admin@chilkatsoft.com"];

success = [mailman SendEmail: email];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// Close the connection with the server.  This closes the tunnel through ssh2.
success = [mailman CloseSmtpConnection];
if (success != YES) {
    NSLog(@"%@",@"Connection to SMTP server not closed cleanly.");
}

NSLog(@"%@",@"Mail Sent!");

// Close the connection with ssh2.  (This closes the the tunnel through ssh1.)
// The connection with ssh1 is still alive, and may be used for more connections.
[ssh2 Disconnect];

[ssh1 Disconnect];