tencent cloud

Feature Overview

The IoT Hub platform provides a broadcast communication topic. The server can publish a broadcast message by calling the broadcast communication API, which can be received by online devices that have subscribed to the broadcast topic under the same product.

Broadcast Topic

The broadcast communication topic is $broadcast/rxd/${ProductId}/${DeviceName}, where ${ProductId} and${DeviceName}` represent the specific product ID and device name.

Broadcast Communication Sample

The sample completes device connection through the device-side C-SDK on Linux and calls APIs together with Tencent Cloud API Explorer. The specific steps are as follows:

Creating device in console

Scenario description

• If you have multiple air conditioner devices connected to the IoT Hub platform, then the server can send the same instruction to all of them for turning off.
• The server calls the PublishBroadcastMessage API and specifies the ProductId and the Payload of the broadcast message. Then, all online devices that have subscribed to the broadcast topic under the product will receive the broadcast message with the Payload.

Creating product and device

Create an air conditioner product and airConditioner1, airConditioner2, and other devices as instructed in Device Interconnection.

Compiling and running demo (with key-authenticated device as example)

1. Compile the SDK

Modify CMakeLists.txt to ensure that the following options exist:

set(BUILD_TYPE                   "release")
set(COMPILE_TOOLS                "gcc") 
set(PLATFORM                      "linux")
set(FEATURE_MQTT_COMM_ENABLED ON)
set(FEATURE_BROADCAST_ENABLED ON)
set(FEATURE_AUTH_MODE "KEY")
set(FEATURE_AUTH_WITH_NOTLS OFF)
set(FEATURE_DEBUG_DEV_INFO_USED  OFF)

Run the following script for compilation:

./cmake_build.sh 

The demo output broadcast_sample is in the output/release/bin folder.

2. Enter the device information

Enter the information of the airConditioner1 device created above in a JSON file aircond_device_info1.json:

{
  "auth_mode":"KEY",    
  "productId":"KL4J2****8",
  "deviceName":"airConditioner1",    
  "key_deviceinfo":{    
      "deviceSecret":"zOZXUaycuwlePt****8dBA=="
  }
}

Enter the information of the airConditioner2 device in another JSON file aircond_device_info2.json:

{
  "auth_mode":"KEY",    
  "productId":"KL4J2****8",
  "deviceName":"airConditioner2",    
  "key_deviceinfo":{    
      "deviceSecret":"+IiVNsyKRh0AW****IE07A=="
  }
}

Enter the information of other devices in corresponding JSON files in turn.

3. Run the broadcast_sample demo

As this scenario involves multiple demos running simultaneously, you can open multiple terminals to run the broadcast_sample demo, and you will see that all the demos subscribe to the $broadcast/rxd/${productID}/${deviceName} topic and are in the waiting status.
The output of the airConditioner1 device is as follows:

./broadcast_sample -c ./aircond_device_info1.json -l 100
INF|2020-08-03 22:50:28|qcloud_iot_device.c|iot_device_info_set(50): SDK_Ver: 3.2.0, Product_ID: KL4J2****8, Device_Name: airConditioner1
DBG|2020-08-03 22:50:28|HAL_TLS_mbedtls.c|HAL_TLS_Connect(200): Setting up the SSL/TLS structure...
DBG|2020-08-03 22:50:28|HAL_TLS_mbedtls.c|HAL_TLS_Connect(242): Performing the SSL/TLS handshake...
DBG|2020-08-03 22:50:28|HAL_TLS_mbedtls.c|HAL_TLS_Connect(243): Connecting to /KL4J2****8.iotcloud.tencentdevices.com/8883...
INF|2020-08-03 22:50:28|HAL_TLS_mbedtls.c|HAL_TLS_Connect(265): connected with /KL4J2****8.iotcloud.tencentdevices.com/8883...
INF|2020-08-03 22:50:28|mqtt_client.c|IOT_MQTT_Construct(113): mqtt connect with id: 9**** success
INF|2020-08-03 22:50:28|broadcast_sample.c|main(197): Cloud Device Construct Success
DBG|2020-08-03 22:50:28|mqtt_client_subscribe.c|qcloud_iot_mqtt_subscribe(142): topicName=$broadcast/rxd/KL4J2****8/airConditioner1|packet_id=*****
INF|2020-08-03 22:50:28|broadcast_sample.c|_mqtt_event_handler(49): subscribe success, packet-id=*****
DBG|2020-08-03 22:50:28|broadcast.c|_broadcast_event_callback(37): broadcast topic subscribe success

The output of the airConditioner2 device is as follows:

./broadcast_sample -c ./aircond_device_info2.json -l 100
INF|2020-08-03 22:51:24|qcloud_iot_device.c|iot_device_info_set(50): SDK_Ver: 3.2.0, Product_ID: KL4J2****8, Device_Name: airConditioner2
DBG|2020-08-03 22:51:24|HAL_TLS_mbedtls.c|HAL_TLS_Connect(200): Setting up the SSL/TLS structure...
DBG|2020-08-03 22:51:24|HAL_TLS_mbedtls.c|HAL_TLS_Connect(242): Performing the SSL/TLS handshake...
DBG|2020-08-03 22:51:24|HAL_TLS_mbedtls.c|HAL_TLS_Connect(243): Connecting to /KL4J2****8.iotcloud.tencentdevices.com/8883...
INF|2020-08-03 22:51:24|HAL_TLS_mbedtls.c|HAL_TLS_Connect(265): connected with /KL4J2****8.iotcloud.tencentdevices.com/8883...
INF|2020-08-03 22:51:25|mqtt_client.c|IOT_MQTT_Construct(113): mqtt connect with id: f**** success
INF|2020-08-03 22:51:25|broadcast_sample.c|main(197): Cloud Device Construct Success
DBG|2020-08-03 22:51:25|mqtt_client_subscribe.c|qcloud_iot_mqtt_subscribe(142): topicName=$broadcast/rxd/KL4J2****8/airConditioner2|packet_id=*****
INF|2020-08-03 22:51:25|broadcast_sample.c|_mqtt_event_handler(49): subscribe success, packet-id=******
DBG|2020-08-03 22:51:25|broadcast.c|_broadcast_event_callback(37): broadcast topic subscribe success

4. Call TencentCloud API PublishBroadcastMessage to send a broadcast message

Go to API Explorer, enter the personal key and device parameter information, select Online Call, and send the request.

5. Observe the message reception of the air conditioners

Observe the printout of the airConditioner1 device, and you can see that the message sent by the server has been received.

DBG|2020-08-03 22:55:32|broadcast.c|_broadcast_message_cb(25): topic=$broadcast/rxd/KL4J2****8/airConditioner1
INF|2020-08-03 22:55:32|broadcast.c|_broadcast_message_cb(26): len=6, topic_msg=closed
INF|2020-08-03 22:55:32|broadcast_sample.c|_broadcast_message_handler(134): broadcast message=closed

Observe the printout of the airConditioner2 device, and you can see that the message sent by the server has also been received.

DBG|2020-08-03 22:55:32|broadcast.c|_broadcast_message_cb(25): topic=$broadcast/rxd/KL4J2****8/airConditioner2
INF|2020-08-03 22:55:32|broadcast.c|_broadcast_message_cb(26): len=6, topic_msg=closed
INF|2020-08-03 22:55:32|broadcast_sample.c|_broadcast_message_handler(134): broadcast message=closed

6. Turn off air conditioner devices

The devices that have received the instruction will parse the instruction for processing.