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Connect your IoT device to the cloud - Virtual IoT Hardware and Raspberry Pi

In this part of the lesson, you will connect your virtual IoT device or Raspberry Pi to your IoT Hub to send telemetry data and receive commands.

Connect your device to IoT Hub

The next step is to connect your device to the IoT Hub.

Task - Connect to IoT Hub

Open the soil-moisture-sensor folder in VS Code. If you are using a virtual IoT device, ensure the virtual environment is running in the terminal.
Install some additional Pip packages:
```
pip3 install azure-iot-device
```
azure-iot-device is a library used to communicate with your IoT Hub.
Add the following imports to the top of the app.py file, just below the existing imports:
```
from azure.iot.device import IoTHubDeviceClient, Message, MethodResponse
```
This code imports the SDK needed to communicate with your IoT Hub.
Remove the import paho.mqtt.client as mqtt line, as this library is no longer required. Delete all the MQTT-related code, including the topic names, any code that uses mqtt_client, and the handle_command function. Keep the while True: loop, but remove the mqtt_client.publish line from this loop.
Add the following code below the import statements:
```
connection_string = "<connection string>"
```
Replace <connection string> with the connection string you retrieved for the device earlier in this lesson.

💁 This is not a best practice. Connection strings should never be stored in source code, as they can be checked into source control and accessed by others. We are doing this here for simplicity. Ideally, you should use something like an environment variable and a tool like python-dotenv. You will learn more about this in a future lesson.

Below this code, add the following to create a device client object that can communicate with the IoT Hub and connect it:

device_client = IoTHubDeviceClient.create_from_connection_string(connection_string)

print('Connecting')
device_client.connect()
print('Connected')

Run this code. You will see your device connect.

pi@raspberrypi:~/soil-moisture-sensor $ python3 app.py 
Connecting
Connected
Soil moisture: 379

Send telemetry

Now that your device is connected, you can send telemetry data to the IoT Hub instead of the MQTT broker.

Task - Send telemetry

Add the following code inside the while True loop, just before the sleep statement:
```
message = Message(json.dumps({ 'soil_moisture': soil_moisture }))
device_client.send_message(message)
```
This code creates an IoT Hub Message containing the soil moisture reading as a JSON string, then sends it to the IoT Hub as a device-to-cloud message.

Handle commands

Your device needs to handle commands from the server code to control the relay. These commands are sent as direct method requests.

Task - Handle a direct method request

Add the following code before the while True loop:
```
def handle_method_request(request):
    print("Direct method received - ", request.name)

    if request.name == "relay_on":
        relay.on()
    elif request.name == "relay_off":
        relay.off()    
```
This defines a method, handle_method_request, which will be called when a direct method is invoked by the IoT Hub. Each direct method has a name, and this code expects a method called relay_on to turn the relay on, and relay_off to turn the relay off.

💁 This could also be implemented as a single direct method request, passing the desired state of the relay in a payload that can be included with the method request and accessed from the request object.
Direct methods require a response to indicate that they have been handled. Add the following code at the end of the handle_method_request function to create a response to the request:
```
method_response = MethodResponse.create_from_method_request(request, 200)
device_client.send_method_response(method_response)
```
This code sends a response to the direct method request with an HTTP status code of 200 and sends it back to the IoT Hub.
Add the following code below this function definition:
```
device_client.on_method_request_received = handle_method_request
```
This code tells the IoT Hub client to call the handle_method_request function whenever a direct method is invoked.

💁 You can find this code in the code/pi or code/virtual-device folder.

😀 Your soil moisture sensor program is now connected to your IoT Hub!

Disclaimer:
This document has been translated using the AI translation service Co-op Translator. While we aim for accuracy, please note that automated translations may include errors or inaccuracies. The original document in its native language should be regarded as the authoritative source. For critical information, professional human translation is advised. We are not responsible for any misunderstandings or misinterpretations resulting from the use of this translation.

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