(Java) TCP Socket through SSH Tunnel (Port Forwarding)

Demonstrates using Chilkat Socket to communicate to a TCP service through an SSH tunnel. This example will connect to an NIST time server and (using the old Time Protocol (RFC 868)), will read the current GMT time.

Note: This is not necessarily a recommended means for getting the current date/time. The most commonly used time protocol is the Network Time Protocol (RFC-1305). The intent of this example is to show how TCP communications can occur through an SSH tunnel.

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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[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkSocket tunnel = new CkSocket();

    String sshHostname = "sftp.example.com";
    int sshPort = 22;

    // Connect to an SSH server and establish the SSH tunnel:
    boolean success = tunnel.SshOpenTunnel(sshHostname,sshPort);
    if (success != true) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    // Authenticate with the SSH server via a login/password
    // or with a public key.
    // This example demonstrates SSH password authentication.
    success = tunnel.SshAuthenticatePw("mySshLogin","mySshPassword");
    if (success != true) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    // OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
    // Once the channel is obtained, the Socket API may
    // be used exactly the same as usual, except all communications
    // are sent through the channel in the SSH tunnel.
    // Any number of channels may be created from the same SSH tunnel.
    // Multiple channels may coexist at the same time.

    // Connect to an NIST time server and read the current date/time
    CkSocket channel;
    int maxWaitMs = 4000;
    boolean useTls = false;
    channel = tunnel.SshOpenChannel("time-c.nist.gov",37,useTls,maxWaitMs);
    if (tunnel.get_LastMethodSuccess() == false) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    // The time server will send a big-endian 32-bit integer representing
    // the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
    // The ReceiveInt32 method will receive a 4-byte integer, but returns
    // true or false to indicate success.  If successful, the integer
    // is obtained via the ReceivedInt property.
    boolean bigEndian = true;
    success = channel.ReceiveInt32(bigEndian);
    if (success != true) {
        System.out.println(channel.lastErrorText());

        return;
        }

    CkDateTime dt = new CkDateTime();
    dt.SetFromNtpTime(channel.get_ReceivedInt());

    // Show the current local date/time
    boolean bLocalTime = true;
    System.out.println("Current local date/time: " + dt.getAsRfc822(bLocalTime));

    // Close the SSH channel.
    success = channel.Close(maxWaitMs);
    if (success != true) {
        System.out.println(channel.lastErrorText());

        return;
        }

    // It is possible to create a new channel from the existing SSH tunnel for the next connection:
    // Any number of channels may be created from the same SSH tunnel.
    // Multiple channels may coexist at the same time.
    channel = tunnel.SshOpenChannel("time-a.nist.gov",37,useTls,maxWaitMs);
    if (tunnel.get_LastMethodSuccess() == false) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    // Review the LastErrorText to see that the connection was made via the SSH tunnel:
    System.out.println(tunnel.lastErrorText());

    // Close the connection to time-a.nist.gov.  This is actually closing our channel
    // within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
    success = channel.Close(maxWaitMs);
    if (success != true) {
        System.out.println(channel.lastErrorText());

        return;
        }

    // Finally, close the SSH tunnel.
    success = tunnel.SshCloseTunnel();
    if (success != true) {
        System.out.println(tunnel.lastErrorText());
        return;
        }

    System.out.println("TCP SSH tunneling example completed.");
  }
}