Cloud2Device Messages

c2d-overview

In order to verify that the device and the cloud connector can successfully receive messages sent by the cloud backend, we will send a dummy message to the device.

Pre-Requisites

Device is up and running, e.g by running in qemu
Eclipse Leda has successfully booted
The device has been provisioned and configured, see Device Provisioning

Validating configuration

First, let’s check that the cloud connection is active.

Login as root
Run sdv-health and check for the SDV Connectivity section:
```
sdv-health
```
Start watching the output of the cloud connector:
```
kantui
```

Select the cloud-connector container and press L to watch the logs

Note: When an unknown type of message is received, the cloud connector will log an error:
2022/04/13 16:04:41.911727  [agent]  ERROR  Handler returned error err="cannot deserialize cloud message: invalid character 'H' looking for beginning of value

Start watching on the MQTT message broker:
```
mosquitto_sub -h localhost -t '#' --pretty -v
```
Note: When a known type of message is received, the cloud connector will forward the message to the MQTT broker into the corresponding topic $appId/$cmdName

Sending a Device Message

Go to the Web Console of Azure IoT Hub
Select the device
Click on “Send Message”
Enter a C2D payload and click “Send”

Alternatively, on command line, use the Azure CLI client. Replace DeviceId and IotHubName with the appropriate names of your IoT Hub and device.

az iot device c2d-message send \
 --device-id ${DeviceID} \
 --hub-name ${IotHubName} \
 --data 'Hello World'