Dart

FTP through SSH Tunnel with Dynamic Port Forwarding

See more FTP Examples

Demonstrates how to start a background thread that runs a portable SSH tunnel w/ dynamic port forwarding that the foreground thread can be used for establishing FTP sessions through an SSH tunnel.

Note: Some developers may be accustomed to starting an stunnel.exe proxy from https://www.stunnel.org. The stunnel.exe is not necessary here. Chilkat's background thread fulfills the task of what the external stunnel.exe does. Therefore, your application is self-contained, meaning that it can run anywhere because the SSH tunnel proxy is built-in.

Dart

import 'package:chilkat/chilkat.dart';

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

  final tunnel = CkSshTunnel();

  final sshHostname = 'sftp.example.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, 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 ftp = CkFtp2();

  // Indicate that the HTTP object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
  ftp.socksHostname = 'localhost';
  // The SocksPort must equal the port passed to BeginAccepting above.
  ftp.socksPort = 1080;
  ftp.socksVersion = 5;
  // The SOCKS5 login/password set here must equal the InboundSocksUsername/Password set above.
  ftp.socksUsername = 'chilkat123';
  ftp.socksPassword = 'password123';

  // This is the actual FTP server domain or IP address, and the login/password for the user account on the destination FTP server.
  ftp.hostname = 'ftp.someFtpServer.com';
  ftp.username = 'myLogin';
  ftp.password = 'myPassword';
  ftp.authTls = true;

  // Connect and login (via the SSH tunnel) to the FTP server.
  try {
    ftp.connect();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Change to the remote directory where the file is located.
  // This step is only necessary if the file is not in the root directory
  // for the FTP account.
  try {
    ftp.changeRemoteDir('junk');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final localFilename = 'c:/temp/hamlet.xml';
  final remoteFilename = 'hamlet.xml';

  // Download a file.  (the data connection is also automatically established through the 
  // SSH tunnel using dynamic port forwarding..)
  try {
    ftp.getFile(remoteFilename, localFilename);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // The disconnect is disconnecting with the FTP server and closes the SSH tunnel.
  // The background tunnel thread is still running, and may be used for subsequent FTP connections,
  // or even connections for any other purpose, such as HTTP, IMAP, SMTP, POP3, etc.
  ftp.disconnect();

  // When the app is finished with the tunnel, it can cleanup..

  // 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;
  }
}