Dart Requires Chilkat v11.0.0+

SSH Tunnel Inside another SSH Tunnel

See more SSH Tunnel Examples

Demonstrates how to create a TCP/IP socket connection through an SSH tunnel that is dynamic port forwarded through another SSH tunnel. Dart

import 'package:chilkat/chilkat.dart';

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

  final tunnel = CkSshTunnel();

  final sshHostname = 'www.ssh-serverA.com';
  final sshPort = 22;

  // Connect to an SSH server and establish the SSH tunnel:
  try {
    tunnel.connect(sshHostname, sshPort);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Authenticate with the SSH server via a login/password
  // or with a public key.  
  // This example demonstrates SSH password authentication.
  try {
    tunnel.authenticatePw('mySshLogin', 'mySshPassword');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
  // with dynamic port forwarding:
  tunnel.dynamicPortForwarding = 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.inboundSocksUsername = 'chilkat123';
  tunnel.inboundSocksPassword = 'password123';

  // Start the listen/accept thread to begin accepting SOCKS proxy client connections.
  // Listen on port 1080.
  try {
    tunnel.beginAccepting(1080);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    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, Socket, 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.

  final tunnelB = CkSocket();

  // Indicate that the socket object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
  tunnelB.socksHostname = 'localhost';
  tunnelB.socksPort = 1080;
  tunnelB.socksVersion = 5;
  tunnelB.socksUsername = 'chilkat123';
  tunnelB.socksPassword = 'password123';

  // Open a new SSH tunnel through the existing tunnel (via what we treat as a SOCKS5 proxy,
  // but it is actually a dynamic port-forwarded SSH tunnel).
  try {
    tunnelB.sshOpenTunnel('www.ssh-serverB.com', 22);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Authenticate with ssh-serverB.com
  try {
    tunnelB.sshAuthenticatePw('uname', 'pwd');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // OK, the SSH tunnel (within a 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
  final channel = CkSocket();
  final maxWaitMs = 4000;
  final useTls = false;
  try {
    tunnelB.sshNewChannel('time-c.nist.gov', 37, useTls, maxWaitMs, channel);
  } on ChilkatException catch (e) {
    print(e.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.
  final bigEndian = true;
  try {
    channel.receiveInt32(bigEndian);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final dt = CkDateTime();
  dt.setFromNtpTime(channel.receivedInt);

  // Show the current local date/time
  final bLocalTime = true;
  print('Current local date/time: ${dt.getAsRfc822(bLocalTime)}');

  // Close the SSH channel.
  try {
    channel.close(maxWaitMs);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Stop the background listen/accept thread:
  final waitForThreadExit = true;
  try {
    tunnel.stopAccepting(waitForThreadExit);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Close the SSH tunnel (would also kick any remaining connected clients).
  try {
    tunnel.closeTunnel(waitForThreadExit);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }
}