public function login($username = 'anonymous', $password = '')
    {
        $result = @ftp_login($this->connection, $username, $password);

        if ($result === false) {
            throw new Exception('Login incorrect');
        } else {
            // set passive mode
            if (!is_null($this->passive)) {
                $this->passive($this->passive);
            }

            return $this;
        }
    }