system_filetransfer_info in drupal-7.x/modules/system/system.module

Implements hook_filetransfer_info().

abstract class FileTransferFTP extends FileTransfer {

  public function __construct($jail, $username, $password, $hostname, $port) {
    $this->username = $username;
    $this->password = $password;
    $this->hostname = $hostname;
    $this->port = $port;
    parent::__construct($jail);
  }

  /**
   * Return an object which can implement the FTP protocol.
   *
   * @param string $jail
   * @param array $settings
   * @return FileTransferFTP
   *   The appropriate FileTransferFTP subclass based on the available
   *   options. If the FTP PHP extension is available, use it.
   */
  static function factory($jail, $settings) {
    $username = empty($settings['username']) ? '' : $settings['username'];
    $password = empty($settings['password']) ? '' : $settings['password'];
    $hostname = empty($settings['advanced']['hostname']) ? 'localhost' : $settings['advanced']['hostname'];
    $port = empty($settings['advanced']['port']) ? 21 : $settings['advanced']['port'];

    if (function_exists('ftp_connect')) {
      $class = 'FileTransferFTPExtension';
    }
    else {
      throw new FileTransferException('No FTP backend available.');
    }

    return new $class($jail, $username, $password, $hostname, $port);
  }

  /**
   * Returns the form to configure the FileTransfer class for FTP.
   */
  public function getSettingsForm() {
    $form = parent::getSettingsForm();
    $form['advanced']['port']['#default_value'] = 21;
    return $form;
  }
}