问题
As a MQTT client (device), I am using devices/{deviceid}/messages/devicebound/# topic to receive Cloud to Device messages. This device is a gateway for me and there are 3 devices attached to it.
I want to send 3 different commands to 1 gateway on 3 different topics, like
devices/{deviceid}/messages/devicebound/device1
devices/{deviceid}/messages/devicebound/device2
devices/{deviceid}/messages/devicebound/device3
My gateway is registered in iot-hub and I use it at {deviceid}.
Is it possible?
回答1:
Based on the official document "Communicate with your IoT hub using the MQTT protocol", it says:
Since IoT Hub is not a general purpose pub-sub messaging broker, it only supports the documented topic names and topic filters.
IoT Hub delivers messages with the Topic Name devices/{device_id}/messages/devicebound/, or devices/{device_id}/messages/devicebound/{property_bag} if there are any message properties.
Here is a solution using system property "messageId" as the filter. So your three topics:
devices/{deviceid}/messages/devicebound/device1
devices/{deviceid}/messages/devicebound/device2
devices/{deviceid}/messages/devicebound/device3
would look like this:
devices/{deviceid}/messages/devicebound/%24.mid=device1&%24.to=%2Fdevices%2Ftest1%2Fmessages%2FdeviceBound&iothub-ack=full
devices/{deviceid}/messages/devicebound/%24.mid=device2&%24.to=%2Fdevices%2Ftest1%2Fmessages%2FdeviceBound&iothub-ack=full
devices/{deviceid}/messages/devicebound/%24.mid=device3&%24.to=%2Fdevices%2Ftest1%2Fmessages%2FdeviceBound&iothub-ack=full
This is the test:
Send C2D message from azure device explorer:
Receive C2D message from MQTTBox:
来源：https://stackoverflow.com/questions/48775383/azure-iot-hub-send-message-c2d-to-one-device-on-2-topics-instead-of-devicebo