Java

SSH Through a SOCKS Proxy

Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy. Set the SOCKS properties before calling Connect, and set SocksVersion to match the proxy server.

Background: SOCKS is a general-purpose TCP relay, so unlike an HTTP proxy it is designed from the start to carry arbitrary protocols — usually the smoother option for SSH. The version matters: SOCKS4 supports only a username with no password, while SOCKS5 supports full login/password authentication as well as IPv6 and remote DNS resolution. Note this is the inverse of dynamic port forwarding: here a SOCKS proxy is used to reach the SSH server, rather than SSH providing a SOCKS proxy.

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import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Ssh;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        // Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy.

        Ssh ssh = new Ssh();

        // Set the SOCKS proxy properties before connecting.  The hostname may be a domain name or an
        // IP address.
        ssh.setSocksHostname("socks.example.com");
        ssh.setSocksPort(1080);
        ssh.setSocksUsername("mySocksLogin");
        ssh.setSocksPassword("mySocksPassword");

        // Set the version to match the proxy server: 4 or 5.
        // Note: SOCKS4 supports only a username, with no password.  SOCKS5 supports full
        // login/password authentication.
        ssh.setSocksVersion(5);

        String hostname = "ssh.example.com";
        int port = 22;
        try {
            ssh.connect(hostname, port);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Connected to the SSH server through the SOCKS proxy.");

        // Normally you would not hard-code the password in source.  You should instead obtain it
        // from an interactive prompt, environment variable, or a secrets vault.
        String password = "mySshPassword";

        try {
            ssh.authenticatePw("mySshLogin", password);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // ... use the SSH connection normally ...

        ssh.disconnect();
    }
}