Command and control - request-response
Request-response commands are sent from a connected business solution through the Bosch IoT Things and Bosch IoT Hub to a connected device.
We assume your device is ready to listen and that you send a command. This will be forwarded automatically to your device.
After the command has been processed by the device, the device indicates the status of execution with a HTTP status code.
Additionally it can send back a generic payload as response to the command.
The application can use request-response type of communication to invoke an action on the device, e.g. "print the barcode" or "water the flowers". After execution the device informs the business application about success or failure of this action.
Schematic view
Prerequisites
At this point we assume that you went through all steps described at Getting started and Telemetry example.
The mosquitto_sub command is installed. See Eclipse Mosquitto.
The mosquitto_pub command is installed. See Eclipse Mosquitto.
Create command subscriber
This step is similar as in the use case with one-way command.
mosquitto_sub -d -h mqtt.bosch-iot-hub.com -p 8883 -u <authId>@<tenantId> -P <your-password> --cafile iothub.crt -k 30 -t command///req/#Make sure you replace all parameters correctly.
Send a message via Things API
Open Suite API docs - Bosch IoT Things HTTP API 2
Authorize with Suite OAuth token.
Message resource
Navigate to POST /things/{thingId}/inbox/messages/{messageSubject}.
Click Try it out to access the entry fields.
Set the thing ID (this is required).
Set the messageSubject (this is required) - in our case it is: "do-something".
Set the timeout (this is required) - in our example we have set it to 60 seconds.
Set the Request body.
The body can be sent in JSON format (choose application/json), octet-stream (choose application/octet-stream) or plain text (choose text/plain).
Our example shows text/plain format.
Click Execute.
You have sent a command which will wait 60 seconds for the response.
Receive a request-response command
You should see the command message printed out on the command line:
Client mosqsub/XXXXXX-XXXXXXS received PUBLISH (d0, q0, r0, m0, 'command///req/024da27b390-9361-4a4e-a272-3ace509c5b59replies/do-something', ... (637 bytes)){ "topic": "<your-namespace>/<your-device-name>/things/live/messages/do-something", "headers": { "correlation-id": "024da27b390-9361-4a4e-a272-3ace509c5b59", "version": 2, "timeout":"60", "accept":"*/*", "host":"things.eu-1.bosch-iot-suite.com", "content-type":"text/plain", "accept-encoding":"gzip, deflate, br", "timestamp":"2019-07-24T15:33:30.588+02:00"} }, "path": "/inbox/messages/do-something", "value": "Execute the task."}The MQTT topic of the published command message command///req/024d...replies/do-something contains in this example the following information:
A request ID (the 024d...replies part of the MQTT topic) - this is the unique ID of the command message for which this answer is for in Bosch IoT Hub.
The message subject is do-something (see last word in the MQTT topic) - it describes the command message sent to the device.
The body of the command message contains in this example the following information:
The payload of the command message.
Send the response from device back to the cloud services
Send the response of the command message using the mosquitto_pub command:
mosquitto_pub -d -h mqtt.bosch-iot-hub.com -p 8883 -u <authId>@<tenantId> -P <your-password> --cafile iothub.crt -k 30 \-t 'command///res/024da27b390-9361-4a4e-a272-3ace509c5b59replies/200' \-m "{\"topic\":\"<your.namespace>/<your-device-name>/things/live/messages/do-something\",\"headers\": {\"correlation-id\": \"024da27b390-9361-4a4e-a272-3ace509c5b59\",\"content-type\":\"text/plain\"},\"path\":\"/inbox/messages/do-something\",\"value\":\"success: true\",\"status\": 200 }"The topic of the response contains in this example the following information:
A request ID (in our example 024da27b390-xxxreplies ) - this is exactly the unique ID of the command for which this answer is for in Bosch IoT Hub.
<authId> the ID of the credential that was created during device provisioning.
<tenantId> the ID of your tenant.
<your-password> the password that was registered with the credential.
The body of the response contains in this example the following information:
The payload of the response.
200 the return status code of message.
Forward the response to the solution (via Things)
Bosch IoT Things automatically applies the change and forwards the received response to the solution.
