private static function singleCall(array $request, Parameters $parameters_object) {

        if ( !isset($request[0]) || !isset($request[1]) ) {

            return self::packError(-32600, $parameters_object->errors()->get(-32600));

        }

        if ( $request[0] == 'system.multicall' ) {

            return self::packError(-31001, $parameters_object->errors()->get(-31001));

        }

        $payload = array($request[0], $request[1]);

        try {

            return XmlProcessor::process($payload, $parameters_object, $parameters_object->logger());

        } catch (RpcException $re) {

            return self::packError($re->getCode(), $re->getMessage());

        } catch (Exception $e) {

            return self::packError(-32500, $re->getMessage());

        }

    }