阿里云的组件包例程到底怎么处理接收的数据控制灯亮灭？在线等 急

static void example_message_arrive(void *pcontext, void *pclient, iotx_mqtt_event_msg_pt msg)
{
    iotx_mqtt_topic_info_t     *topic_info = (iotx_mqtt_topic_info_pt) msg->msg;
    static rt_base_t led_state = PIN_LOW;
    switch (msg->event_type) {
        case IOTX_MQTT_EVENT_PUBLISH_RECEIVED:
            /* print topic name and topic message */
            EXAMPLE_TRACE("Message Arrived:");
            EXAMPLE_TRACE("Topic  : %.*s", topic_info->topic_len, topic_info->ptopic);
            EXAMPLE_TRACE("Payload: %.*s", topic_info->payload_len, topic_info->payload);
            EXAMPLE_TRACE("\n");
            rt_int32_t rec=rt_strcmp(topic_info->payload,"led");
            if(rec==0){
                // 反转当前的 LED 状态
                if (led_state == PIN_LOW) {
                    led_state = PIN_HIGH;
                } else {
                    led_state = PIN_LOW;
                }
                rt_pin_write(GPIO_LED_R, led_state);
            }
            break;
        default:
            break;
    }
}