Dart Requires Chilkat v11.0.0+

WebSocket through SSH Tunnel

See more WebSocket Examples

This example shows how to establish a WebSocket connection through an SSH tunnel. The WebSocket protocol communications will be encapsulated within an 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.

  // --------------------------------------------------
  // This example borrows the code from the REST through SSH Tunnel example.
  // We first use the Chilkat Socket object to establish a connection to the WebSocket server through an SSH Tunnel.
  // Next, the Rest object uses the Socket object for its connection.
  // Finally, the WebSocket object uses the Rest object for its connection.  
  // 
  // Hopefully the flexibility of this architecture is easy to see.  All of the HTTP functionality of the Rest object,
  // such as HTTP authentication, custom headers, etc. is available to the WebSocket.  Likewise, all of the advanced functionality
  // of the Socket object is in turn available to the Rest object.  

  // The high-level steps for accomplishing the task of running the WebSocket protocol through an SSH accomplished as follows:
  // 1) Create the SSH tunnel using Chilkat Socket.
  // 2) Open a port-forwarding channel (to the WebSocket server) within the tunnel.
  // 2) Tell Rest to use the Socket object.
  // 3) Tell WebSocket to use the Rest object.

  final tunnel = CkSocket();

  final sshHostname = 'sftp.example.com';
  final sshPort = 22;

  // Connect to an SSH server and establish the SSH tunnel:
  try {
    tunnel.sshOpenTunnel(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.sshAuthenticatePw('mySshLogin', 'mySshPassword');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  //  OK, the SSH tunnel is setup.  Now open a channel within the tunnel.

  final bTls = true;
  final port = 443;
  final maxWaitMs = 5000;

  // This returns a socket object that is a single channel within the SSH tunnel.
  // The SSH channel is our logical port-forwarded connection through the SSH tunnel.
  // Note: This example establishes a TLS connection to the target WebSocket server.
  // (The TLS protocol will run on the logical channel within the SSH tunnel.)
  // Your application can just as easily make a non-TLS connection by changing the arguments
  // passed to SshNewChannel.
  final channel = CkSocket();
  try {
    tunnel.sshNewChannel('some-websocket-server.com', port, bTls, maxWaitMs, channel);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Create a REST object and tell it to use the SSH channel.
  // This connection is a TLS running on an SSH channel through an SSH tunnel.
  // In other words, TLS is wrapped within the SSH tunnel.
  final rest = CkRest();
  try {
    rest.useConnection(channel, false);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Finally, tell our WebSocket object to use the Rest object..
  final ws = CkWebSocket();

  // Tell the WebSocket to use this connection.
  try {
    ws.useConnection(rest);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Add the standard WebSocket open handshake headers that will be needed.
  // (This adds the required HTTP request headers to the rest object.)
  ws.addClientHeaders();

  // Add any additional headers that might be desired.
  // Two common WebSocketSpecific headers are "Sec-WebSocket-Protocol" and "Origin".
  rest.addHeader('Sec-WebSocket-Protocol', 'x-some-websocket-subprotocol');
  rest.addHeader('Origin', 'http://some-websocket-server.com');

  // Do the open handshake.
  final String responseBody;
  try {
    responseBody = rest.fullRequestNoBody('GET', '/something');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // If successful, the HTTP response status code should be 101,
  // and the response body will be empty. (If it failed, we'll have a look
  // at the response body..)
  final statusCode = rest.responseStatusCode;
  print('Response status code: $statusCode');

  if (statusCode != 101) {
    print(responseBody);
    print('-- Failed because of unexpected response status code.');
    return;
  }

  // We have the expected 101 response, so let's now validate the 
  // contents of the response, such as the value sent by the server in the
  // Sec-WebSocket-Accept header. 
  try {
    ws.validateServerHandshake();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('WebSocket connection successful.');

  // The application may now begin sending and receiving frames on the WebSocket connection.
  // (At this point, we're done with the rest object...)
}