Dart

TCP or TLS over Multiple Hop SSH to Remote Server

See more Socket/SSL/TLS Examples

Demonstrates how to use the Chilkat Socket API to connect to a remote server (using TCP or TLS) tunneled through mulitple-hop SSH. The scheme looks like this:

Application => ServerSSH1 => ServerSSH2 => DestinationServer

The ConnectThroughSsh and UseSsh methods are added in Chilkat version 9.5.0.55 to accomplish this task.

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 ssh1 = CkSsh();

  // Connect directly to the 1st SSH server.
  try {
    ssh1.connect('serverssh1.com', 22);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Authenticate using login/password:
  try {
    ssh1.authenticatePw('ssh1Login', 'ssh1Password');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Connect through the 1st SSH connection to reach a 2nd SSH server.
  // Note: Any number of SSH connections may be simultaneously tunneled through a single
  // existing SSH connection.
  final ssh2 = CkSsh();
  try {
    ssh2.connectThroughSsh(ssh1, 'serverssh2.com', 22);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Authenticate with ssh2...
  try {
    ssh2.authenticatePw('ssh2Login', 'ssh2Password');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final socket = CkSocket();

  // Tell the socket object to connect to our destination server though the ssh2 tunnel (which itself is routed through ssh1).
  // The connection looks like this:  ApplicationSocket(TLS) => ServerSSH1 => ServerSSH2 => DestinationServer
  try {
    socket.useSsh(ssh2);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Connect using TLS to www.chilkatsoft.com
  // We could also tunnel a bare TCP connection by specifying port 80 with useTls = false.
  final useTls = true;
  final maxWaitMillisec = 20000;
  try {
    socket.connect('www.chilkatsoft.com', 443, useTls, maxWaitMillisec);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Once the multiple hop SSH tunneled connection is setup,  the socket programming
  // is identical to the normal case where we have a direct connection.

  // Tell the socket object that all text is to be sent in the utf-8 encoding,
  // and the text received is assumed to be utf-8.
  socket.stringCharset = 'utf-8';

  // Send an HTTP HEAD request:
  try {
    socket.sendString('HEAD / HTTP/1.1\r\nHost: www.chilkatsoft.com\r\n\r\n');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Wait a maximum of 4 seconds while no data is forthcoming:
  socket.maxReadIdleMs = 4000;

  // Get the 1st response line, which should be "HTTP/1.1 200 OK"
  final String responseStatusLine;
  try {
    responseStatusLine = socket.receiveToCRLF();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('StatusLine: $responseStatusLine');

  // Now get the 1st line of the response header:
  final String responseHeaderLine;
  try {
    responseHeaderLine = socket.receiveToCRLF();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('HeaderLine: $responseHeaderLine');

  // Now read the remainder of the response header by reading until a double CRLF is seen:
  final String remainderOfHeader;
  try {
    remainderOfHeader = socket.receiveUntilMatch('\r\n\r\n');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Remainder: $remainderOfHeader');

  // Close the connection with the server.  This closes the tunnel through ssh2.
  // Wait a max of 20 seconds (20000 millsec)
  socket.close(20000);

  // Close the connection with ssh2.  (This closes the the tunnel through ssh1.)
  // The connection with ssh1 is still alive, and may be used for more connections.
  ssh2.disconnect();

  ssh1.disconnect();
}