public static function forge($host = null, $user = null, $password = null, $port = 21, $timeout = 90)
        {
            static::$_host = $host;
            static::$_user = $user;
            static::$_pwd = $password;
            static::$_port = (int)$port;
            static::$_timeout = (int)$timeout;

            if(!static::$instance) {
                static::$instance = new self();
            }

            return static::$instance;
        }