Java

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. Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  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.
    CkMailMan mailman = new CkMailMan();

    //  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).
    String sshHostname = "sftp.example.com";
    int sshPort = 22;

    //  Connect to an SSH server and establish the SSH tunnel:
    success = mailman.SshOpenTunnel(sshHostname,sshPort);
    if (success == false) {
        System.out.println(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","ssh_password");
    if (success == false) {
        System.out.println(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.put_MailHost("mail.my-pop3-server.com");

    //  Set the POP3 settings for your POP3 server:
    mailman.put_PopUsername("pop3_login");
    mailman.put_PopPassword("pop3_password");
    mailman.put_MailPort(995);
    mailman.put_PopSsl(true);

    //  Connect to the POP3 server through the already-established SSH tunnel:
    success = mailman.Pop3BeginSession();
    if (success == false) {
        System.out.println(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.
    System.out.println(mailman.lastErrorText());

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

    if (numToDownload == 0) {
        System.out.println("No messages in the POP3 inbox.");
        return;
        }

    //  Download a max of 5 messages
    int i;
    CkEmail email = new CkEmail();
    for (i = 1; i <= numToDownload; i++) {
        success = mailman.FetchOne(false,0,i,email);
        if (success == false) {
            System.out.println(mailman.lastErrorText());
            return;
            }

        System.out.println(email.ck_from());
        System.out.println(email.subject());
        System.out.println("----");
        }

    //  Close the connection with the POP3 server, leaving the SSH tunnel open for subsequent POP3 connections.
    success = mailman.Pop3EndSession();
    if (success == false) {
        System.out.println(mailman.lastErrorText());
        return;
        }

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

    //  Set the POP3 settings for your POP3 server:
    mailman.put_PopUsername("pop3_login2");
    mailman.put_PopPassword("pop3_password2");
    mailman.put_MailPort(110);
    mailman.put_PopSsl(false);

    success = mailman.Pop3BeginSession();
    if (success == false) {
        System.out.println(mailman.lastErrorText());
        return;
        }

    //  Review the LastErrorText to see that the connection was made via the SSH tunnel:
    System.out.println(mailman.lastErrorText());

    success = mailman.Pop3EndSession();
    if (success == false) {
        System.out.println(mailman.lastErrorText());
        return;
        }

    //  Close the SSH tunnel.
    success = mailman.SshCloseTunnel();
    if (success == false) {
        System.out.println(mailman.lastErrorText());
        return;
        }
  }
}