(Objective-C) POP3 SSH Tunneling (Port Forwarding)

Demonstrates how to connect to a POP3 server through an SSH tunnel. Reads a POP3 mailbox and display the FROM and SUBJECT header fields of each email.

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

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

// The mailman object is used for receiving (POP3) 
// and sending (SMTP) email.
CkoMailMan *mailman = [[CkoMailMan alloc] init];

// The SSH hostname may be a hostname or an 
// IP address, such as "192.168.1.108".
// The port is typically 22 (the standard port for SSH).
NSString *sshHostname = @"sftp.example.com";
int sshPort = 22;

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

// Authenticate with the SSH server via a login/password
// or with a public key.
// This example demonstrates SSH password authentication.
// Note: This is not authenticating with the POP3 server, it is
// for authenticating with the SSH server, which is separate.
success = [mailman SshAuthenticatePw: @"ssh_login" sshPassword: @"ssh_password"];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// OK, the SSH tunnel is setup.  The mailman may
// be used exactly the same as usual, except all communications
// are now sent through the SSH tunnel.

// The SSH tunnel may be kept open for any number of 
// POP3 connections.  

// Set the POP3 server's hostname
mailman.MailHost = @"mail.my-pop3-server.com";

// Set the POP3 settings for your POP3 server:
mailman.PopUsername = @"pop3_login";
mailman.PopPassword = @"pop3_password";
mailman.MailPort = [NSNumber numberWithInt:995];
mailman.PopSsl = YES;

// Connect to the POP3 server through the already-established SSH tunnel:
success = [mailman Pop3BeginSession];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// A visual inspection of the LastErrorText after
// a successful POP3 connection will confirm the SSH tunneling.
// Note: If the POP3 connection uses SSL/TLS, then the SSL/TLS 
// secure channel will be wrapped within the SSH tunnel.
NSLog(@"%@",mailman.LastErrorText);

// How many messages are in the POP3 inbox?
int numToDownload = [[mailman GetMailboxCount] intValue];
if (numToDownload > 5) {
    numToDownload = 5;
}

if (numToDownload == 0) {
    return;
}

// Download a max of 5 messages
int i;
CkoEmail *email = 0;
for (i = 1; i <= numToDownload; i++) {
    email = [mailman FetchByMsgnum: [NSNumber numberWithInt: i]];
    if (mailman.LastMethodSuccess == NO) {
        NSLog(@"%@",mailman.LastErrorText);
        return;
    }

    NSLog(@"%@",email.From);
    NSLog(@"%@",email.Subject);
    NSLog(@"%@",@"----");

}

// Close the connection with the POP3 server, leaving the SSH tunnel open for subsequent POP3 connections.
success = [mailman Pop3EndSession];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// Try connecting to a different POP3 server through the same aleady setup SSH tunnel:
// Set the POP3 server's hostname
mailman.MailHost = @"mail.my-pop3-server2.com";

// Set the POP3 settings for your POP3 server:
mailman.PopUsername = @"pop3_login2";
mailman.PopPassword = @"pop3_password2";
mailman.MailPort = [NSNumber numberWithInt:110];
mailman.PopSsl = NO;

success = [mailman Pop3BeginSession];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// Review the LastErrorText to see that the connection was made via the SSH tunnel:
NSLog(@"%@",mailman.LastErrorText);

success = [mailman Pop3EndSession];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// Close the SSH tunnel.
success = [mailman SshCloseTunnel];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}