(Go) 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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    // 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.
    mailman := chilkat.NewMailMan()

    // 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).
    sshHostname := "sftp.example.com"
    sshPort := 22

    // Connect to an SSH server and establish the SSH tunnel:
    success := mailman.SshOpenTunnel(sshHostname,sshPort)
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        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 != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        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.SetMailHost("mail.my-pop3-server.com")

    // Set the POP3 settings for your POP3 server:
    mailman.SetPopUsername("pop3_login")
    mailman.SetPopPassword("pop3_password")
    mailman.SetMailPort(995)
    mailman.SetPopSsl(true)

    // Connect to the POP3 server through the already-established SSH tunnel:
    success = mailman.Pop3BeginSession()
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        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.
    fmt.Println(mailman.LastErrorText())

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

    if numToDownload == 0 {
        mailman.DisposeMailMan()
        return
    }

    // Download a max of 5 messages
    var i int
    // email is a Email
    for i = 1; i <= numToDownload; i++ {
        email := mailman.FetchByMsgnum(i)
        if mailman.LastMethodSuccess() == false {
            fmt.Println(mailman.LastErrorText())
            mailman.DisposeMailMan()
            return
        }

        fmt.Println(email.From())
        fmt.Println(email.Subject())
        fmt.Println("----")
        email.DisposeEmail()
    }

    // Close the connection with the POP3 server, leaving the SSH tunnel open for subsequent POP3 connections.
    success = mailman.Pop3EndSession()
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        return
    }

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

    // Set the POP3 settings for your POP3 server:
    mailman.SetPopUsername("pop3_login2")
    mailman.SetPopPassword("pop3_password2")
    mailman.SetMailPort(110)
    mailman.SetPopSsl(false)

    success = mailman.Pop3BeginSession()
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        return
    }

    // Review the LastErrorText to see that the connection was made via the SSH tunnel:
    fmt.Println(mailman.LastErrorText())

    success = mailman.Pop3EndSession()
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        return
    }

    // Close the SSH tunnel.
    success = mailman.SshCloseTunnel()
    if success != true {
        fmt.Println(mailman.LastErrorText())
        mailman.DisposeMailMan()
        return
    }


    mailman.DisposeMailMan()