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FTP through SSH Tunnel with Dynamic Port Forwarding

See more FTP Examples

Demonstrates how to start a background thread that runs a portable SSH tunnel w/ dynamic port forwarding that the foreground thread can be used for establishing FTP sessions through an SSH tunnel.

Note: Some developers may be accustomed to starting an stunnel.exe proxy from https://www.stunnel.org. The stunnel.exe is not necessary here. Chilkat's background thread fulfills the task of what the external stunnel.exe does. Therefore, your application is self-contained, meaning that it can run anywhere because the SSH tunnel proxy is built-in.

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

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

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

    const tunnel = try chilkat.SshTunnel.init();
    defer tunnel.deinit();

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

    // Connect to an SSH server and establish the SSH tunnel:
    tunnel.connect(ssh_hostname, ssh_port) catch {
        std.debug.print("{s}\n", .{try tunnel.getLastErrorText(alloc)});
        return;
    };

    // Authenticate with the SSH server via a login/password
    // or with a public key.
    // This example demonstrates SSH password authentication.
    tunnel.authenticatePw("mySshLogin", "mySshPassword") catch {
        std.debug.print("{s}\n", .{try tunnel.getLastErrorText(alloc)});
        return;
    };

    // Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
    // with dynamic port forwarding:
    tunnel.setDynamicPortForwarding(true);

    // We may optionally require that connecting clients authenticate with our SOCKS proxy server.
    // To do this, set an inbound username/password.  Any connecting clients would be required to
    // use SOCKS5 with the correct username/password.
    // If no inbound username/password is set, then our SOCKS proxy server will accept both
    // SOCKS4 and SOCKS5 unauthenticated connections.

    tunnel.setInboundSocksUsername("chilkat123");
    tunnel.setInboundSocksPassword("password123");

    // Start the listen/accept thread to begin accepting SOCKS proxy client connections.
    // Listen on port 1080.
    tunnel.beginAccepting(1080) catch {
        std.debug.print("{s}\n", .{try tunnel.getLastErrorText(alloc)});
        return;
    };

    // Now that a background thread is running a SOCKS proxy server that forwards connections
    // through an SSH tunnel, it is possible to use any Chilkat implemented protocol that is SOCKS capable,
    // such as HTTP, POP3, SMTP, IMAP, FTP, etc.  The protocol may use SSL/TLS because the SSL/TLS
    // will be passed through the SSH tunnel to the end-destination.  Also, any number of simultaneous
    // connections may be routed through the SSH tunnel.

    const ftp = try chilkat.Ftp2.init();
    defer ftp.deinit();

    // Indicate that the HTTP object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
    ftp.setSocksHostname("localhost");
    // The SocksPort must equal the port passed to BeginAccepting above.
    ftp.setSocksPort(1080);
    ftp.setSocksVersion(5);
    // The SOCKS5 login/password set here must equal the InboundSocksUsername/Password set above.
    ftp.setSocksUsername("chilkat123");
    ftp.setSocksPassword("password123");

    // This is the actual FTP server domain or IP address, and the login/password for the user account on the destination FTP server.
    ftp.setHostname("ftp.someFtpServer.com");
    ftp.setUsername("myLogin");
    ftp.setPassword("myPassword");
    ftp.setAuthTls(true);

    // Connect and login (via the SSH tunnel) to the FTP server.
    ftp.connect() catch {
        std.debug.print("{s}\n", .{try ftp.getLastErrorText(alloc)});
        return;
    };

    // Change to the remote directory where the file is located.
    // This step is only necessary if the file is not in the root directory
    // for the FTP account.
    ftp.changeRemoteDir("junk") catch {
        std.debug.print("{s}\n", .{try ftp.getLastErrorText(alloc)});
        return;
    };

    const local_filename = "c:/temp/hamlet.xml";
    const remote_filename = "hamlet.xml";

    // Download a file.  (the data connection is also automatically established through the
    // SSH tunnel using dynamic port forwarding..)
    ftp.getFile(remote_filename, local_filename) catch {
        std.debug.print("{s}\n", .{try ftp.getLastErrorText(alloc)});
        return;
    };

    // The disconnect is disconnecting with the FTP server and closes the SSH tunnel.
    // The background tunnel thread is still running, and may be used for subsequent FTP connections,
    // or even connections for any other purpose, such as HTTP, IMAP, SMTP, POP3, etc.
    try ftp.disconnect();

    // When the app is finished with the tunnel, it can cleanup..

    // Stop the background listen/accept thread:
    const wait_for_thread_exit = true;
    tunnel.stopAccepting(wait_for_thread_exit) catch {
        std.debug.print("{s}\n", .{try tunnel.getLastErrorText(alloc)});
        return;
    };

    // Close the SSH tunnel (would also kick any remaining connected clients).
    tunnel.closeTunnel(wait_for_thread_exit) catch {
        std.debug.print("{s}\n", .{try tunnel.getLastErrorText(alloc)});
        return;
    };
}