What components form the device connection string for a Downstream Device?

The components that form the device connection string for a Downstream Device include essential elements that enable the device to authenticate and establish a secure connection with an Azure IoT Hub. The correct answer consists of HostName, DeviceId, SharedAccessKey, and GatewayHostName.

The HostName is specific to the IoT Hub that the device is connecting to and provides the necessary endpoint for establishing communication. DeviceId uniquely identifies the device within the IoT Hub, allowing the hub to recognize and manage the device. The SharedAccessKey is a security credential that verifies the identity of the device and ensures that only authorized devices can connect to the IoT Hub.

Lastly, the GatewayHostName is included for devices connected through a gateway, helping them route their messages through the gateway to the IoT Hub, especially in scenarios where there are multiple devices behind a single gateway. Thus, this combination of elements in the connection string is crucial for successfully connecting a downstream device to Azure IoT services.

Other combinations, such as only including DeviceId, SharedAccessKey, and a GatewayHostName or using terms like IP address, do not encapsulate all necessary components for connection authentication and routing, thus making them incomplete for a proper device connection string.