Dart

SSH Through a SOCKS Proxy

Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy. Set the SOCKS properties before calling Connect, and set SocksVersion to match the proxy server.

Background: SOCKS is a general-purpose TCP relay, so unlike an HTTP proxy it is designed from the start to carry arbitrary protocols — usually the smoother option for SSH. The version matters: SOCKS4 supports only a username with no password, while SOCKS5 supports full login/password authentication as well as IPv6 and remote DNS resolution. Note this is the inverse of dynamic port forwarding: here a SOCKS proxy is used to reach the SSH server, rather than SSH providing a SOCKS proxy.

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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.

  // Demonstrates connecting to an SSH server through a SOCKS4 or SOCKS5 proxy.

  final ssh = CkSsh();

  // Set the SOCKS proxy properties before connecting.  The hostname may be a domain name or an
  // IP address.
  ssh.socksHostname = 'socks.example.com';
  ssh.socksPort = 1080;
  ssh.socksUsername = 'mySocksLogin';
  ssh.socksPassword = 'mySocksPassword';

  // Set the version to match the proxy server: 4 or 5.
  // Note: SOCKS4 supports only a username, with no password.  SOCKS5 supports full
  // login/password authentication.
  ssh.socksVersion = 5;

  final hostname = 'ssh.example.com';
  final port = 22;
  try {
    ssh.connect(hostname, port);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Connected to the SSH server through the SOCKS proxy.');

  // Normally you would not hard-code the password in source.  You should instead obtain it
  // from an interactive prompt, environment variable, or a secrets vault.
  final password = 'mySshPassword';

  try {
    ssh.authenticatePw('mySshLogin', password);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // ... use the SSH connection normally ...

  ssh.disconnect();
}