广播消息下发

例程讲解

1. 设备端开发

   默认地， 从云端下推的广播消息设备无需订阅topic就能收到。 如果业务上需要将广播的topic和自己的某个MQTT回调函数匹配， 那么使用以下topic即可。

   /sys/${product_key}/${device_name}/broadcast/request/+

   设备收到云端的广播消息后， 按自己业务进行处理即可。

   如demos/mqtt_broadcast_demo.c所示， 在demo_mqtt_default_recv_handler中将简单打印收到的广播消息。

   ...
           case AIOT_MQTTRECV_PUB: {
               printf("pub, qos: %d, topic: %.*s\n", packet->data.pub.qos, packet->data.pub.topic_len, packet->data.pub.topic);
               printf("pub, payload: %.*s\n", packet->data.pub.payload_len, packet->data.pub.payload);
               /* TODO: 处理服务器下发的业务报文, 此处打印broadcast的报文 */
               /* 值得注意的是, 云端下发的广播topic格式为 /sys/${product_key}/${device_name}/broadcast/request/+ */
           }
           break;
   ...

   编译SDK， 运行./output/mqtt-broadcast-demo。

   [1583135792.733][LK-0313] MQTT user calls aiot_mqtt_connect api, connect
   [1583135792.733][LK-0317] mqtt_broadcast_demo&a13FNXXXXXX
   [1583135792.733][LK-0318] 3FC4A3DED5AC5F31C4969CBB1868758B17FAB2E5070FC51C98809104725500E3
   [1583135792.733][LK-0319] a13FNXXXXXX.mqtt_broadcast_demo|timestamp=2524608000000,_ss=1,_v=sdk-c-4.0.0,securemode=2,signmethod=hmacsha256,ext=1,|
   establish mbedtls connection with server(host='a13FNXXXXXX.iot-as-mqtt.cn-shanghai.aliyuncs.com', port=[443])
   success to establish mbedtls connection, fd = 6(cost 44763 bytes in total, max used 47675 bytes)
   [1583135792.888][LK-0313] MQTT connect success in 147 ms
   AIOT_MQTTEVT_CONNECT
   heartbeat response
   ...

2. 调用云端SDK向设备发送广播报文

   云端SDK参考

   使用云端SDK调用Broadcast

   这里为了配合设备端进行演示， 云端SDK调用代码如下：

   PubBroadcastRequest request = new PubBroadcastRequest();
   request.setProductKey("a13FNXXXXXX");
   request.setMessageContent(Base64.getEncoder().encodeToString("receive broadcast from cloud".getBytes()));
   PubBroadcastResponse response = client.getAcsResponse(request);
   System.out.println("PubBroadcastResponse\n" + new Gson().toJson(response) + "\n");

   调用完成后， 云端SDK日志如下：

   {"requestId":"642A8CAB-6205-4F50-9E03-5F56947B52D4","success":true}

   调用完成后， 设备端日志如下：

   [1583135985.622][LK-0309] pub: /sys/a13FNXXXXXX/mqtt_broadcast_demo/broadcast/request/1234387906840325632
   [LK-030A] < 72 65 63 65 69 76 65 20  62 72 6F 61 64 63 61 73 | receive broadcas
   [LK-030A] < 74 20 66 72 6F 6D 20 63  6C 6F 75 64             | t from cloud
   pub, qos: 0, topic: /sys/a13FNXXXXXX/mqtt_broadcast_demo/broadcast/request/1234387906840325632
   pub, payload: receive broadcast from cloud

   从上面云端和设备端的日志可以看出， 设备端收到了云端的一条广播消息receive broadcast from cloud. 至此， Broadcast功能调用完成。

常见错误

广播消息发送过快， 被云端限流. 建议广播发送频率不要超过每分钟1次。

{
    "requestId":"61AD9495-6A88-4B88-BB62-8E1F235C44A9",
    "success":false,
    "code":"iot。messagebroker。RateLimit"
}