Zig Requires Chilkat v11.0.0+

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. Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // 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.
    const mailman = try chilkat.MailMan.init();
    defer mailman.deinit();

    // 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).
    const ssh_hostname = "sftp.example.com";
    const ssh_port = 22;

    // Connect to an SSH server and establish the SSH tunnel:
    mailman.sshOpenTunnel(ssh_hostname, ssh_port) catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        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.
    mailman.sshAuthenticatePw("ssh_login", "ssh_password") catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        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:
    mailman.pop3BeginSession() catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        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.
    std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});

    // How many messages are in the POP3 inbox?
    var num_to_download: i32 = mailman.getMailboxCount();
    if (num_to_download > 5) {
        num_to_download = 5;
    }

    if (num_to_download == 0) {
        std.debug.print("No messages in the POP3 inbox.\n", .{});
        return;
    }

    // Download a max of 5 messages
    var i: i32 = 0;
    const email = try chilkat.Email.init();
    defer email.deinit();
    i = 1;
    while (i <= num_to_download) : (i += 1) {
        mailman.fetchOne(false, 0, i, email) catch {
            std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
            return;
        };

        std.debug.print("{s}\n", .{try email.getFrom(alloc)});
        std.debug.print("{s}\n", .{try email.getSubject(alloc)});
        std.debug.print("----\n", .{});
    }

    // Close the connection with the POP3 server, leaving the SSH tunnel open for subsequent POP3 connections.
    mailman.pop3EndSession() catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        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);

    mailman.pop3BeginSession() catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        return;
    };

    // Review the LastErrorText to see that the connection was made via the SSH tunnel:
    std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});

    mailman.pop3EndSession() catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        return;
    };

    // Close the SSH tunnel.
    mailman.sshCloseTunnel() catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        return;
    };
}