Java

Open a direct-tcpip Channel (SSH Port Forwarding)

Demonstrates the Chilkat Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel through the SSH server to a target host and port. The first argument is the target hostname and the second is the target port. It returns the channel number, or -1 on failure.

Background: This is SSH local port forwarding at the API level: the channel carries ordinary TCP traffic to a service that may be reachable only from the SSH server's network — a database, an internal web app, a message broker. The key detail is that the server resolves the target name, not your machine, so it must resolve and be reachable there. Supplying a numeric IPv4 address avoids remote DNS resolution entirely.

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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;

    //  Demonstrates the Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel
    //  through the SSH server to a target host and port.  The 1st argument is the target hostname
    //  and the 2nd is the target port.  It returns the channel number, or -1 on failure.

    CkSsh ssh = new CkSsh();

    int sshPort = 22;
    success = ssh.Connect("ssh.example.com",sshPort);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  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";

    success = ssh.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  The target name is resolved by the SSH server, not by this computer, so it must be
    //  reachable from the server's network.
    String targetHostname = "db.internal.example.com";
    int targetPort = 5432;
    int channelNum = ssh.OpenDirectTcpIpChannel(targetHostname,targetPort);
    if (channelNum < 0) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    System.out.println("Opened direct-tcpip channel: " + channelNum);

    //  The channel now carries ordinary TCP data to the target, tunneled over SSH.

    ssh.Disconnect();
  }
}