Azure IoT Hub Nodes

Azure IoT Hub is Microsoft's managed cloud service for bidirectional communication between IoT devices and the cloud. MaestroHub provides D2C Send and Twin Report nodes to push data and state updates from pipelines into Azure IoT Hub.

Configuration Quick Reference

Field	What you choose	Details
Parameters	Connection, Function, Function Parameters, Timeout Override	Select the connection profile, function, configure function parameters with expression support, and optionally override timeout.
Settings	Description, Timeout (seconds), Retry on Timeout, Retry on Fail, On Error	Node description, maximum execution time, retry behavior on timeout or failure, and error handling strategy. All execution settings default to pipeline-level values.

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Azure IoT Hub D2C Send Node

Azure IoT Hub D2C Send Node

Send device-to-cloud telemetry messages to Azure IoT Hub from within a pipeline. Use this node to forward sensor readings, aggregated data, or processed events to the cloud for routing, analytics, and storage.

Supported Function Types:

Function Name	Purpose	Common Use Cases
D2C Send (iothub.d2c.send)	Publish telemetry messages to Azure IoT Hub	Sensor data upload, event forwarding, telemetry distribution

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	Azure IoT Hub connection profile to use
Function	Selection	Yes	D2C Send function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema. See your Azure IoT Hub connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

Function parameters for D2C Send:

Parameter	Type	Required	Default	Description
data	String (JSON)	Yes	-	JSON payload to send as D2C telemetry. Use expressions like {{ $input.payload }} for dynamic data from upstream nodes.
contentType	String	No	application/json	MIME type of the payload. Set to application/json for JSON message routing.
contentEncoding	String	No	utf-8	Character encoding of the payload.
qos	Number	No	1	MQTT QoS level: 0 (at most once) or 1 (at least once). Azure IoT Hub does not support QoS 2.
properties	Object	No	-	Key-value pairs for Azure IoT Hub message routing. Example: {"messageType": "telemetry", "source": "line-01"}

All function parameters support expression syntax ({{ expression }}) for dynamic values from the pipeline context.

Input

The node receives the output of the previous node as input. If the data parameter is not explicitly set in the function configuration, the node passes the pipeline input directly as the data payload. Use expressions like {{ $input.payload }} to select specific fields from upstream output.

Output Structure

On success the node produces:

{
  "success": true,
  "functionId": "aef374c3-aa2b-454e-aabc-5657faac5950",
  "data": {
    "bytesWritten": 156,
    "topic": "devices/my-device/messages/events/?$.ct=application/json;charset=utf-8&$.ce=utf-8&messageType=telemetry",
    "qos": 1
  },
  "durationMs": 45,
  "timestamp": "2026-04-03T10:30:45Z"
}

Field	Type	Description
success	boolean	true when the D2C message was published successfully
functionId	string	ID of the executed function
data	object	Publish result details (see below)
durationMs	number	Execution time in milliseconds
timestamp	string	ISO 8601 / RFC 3339 UTC timestamp

data fields:

Field	Type	Description
bytesWritten	number	Size of the published message payload in bytes
topic	string	The full MQTT topic the message was published to, including routing properties
qos	number	The QoS level used for the publish (0 or 1)

Payload Size Limit

Azure IoT Hub enforces a maximum D2C message size of 256 KB. Messages exceeding this limit will fail with a validation error. If your payload is large, consider splitting it across multiple messages or compressing the data.

Store & Forward Behavior

When Store & Forward is enabled on the connection and a D2C publish fails (network error, timeout), the message is automatically buffered in a local queue. The queue drains every 5 seconds when connectivity is restored. Messages have a configurable TTL and the queue respects the Store & Forward Max Items limit set on the connection.

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Azure IoT Hub Twin Report Node

Azure IoT Hub Twin Report Node

Update Device Twin reported properties in Azure IoT Hub from within a pipeline. Use this node to synchronize the device's current state, capabilities, or metadata with the cloud.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Twin Report (iothub.twin.report)	Update reported properties in the Device Twin	State synchronization, firmware version reporting, configuration acknowledgment

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	Azure IoT Hub connection profile to use
Function	Selection	Yes	Twin Report function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema. See your Azure IoT Hub connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

Function parameters for Twin Report:

Parameter	Type	Required	Default	Description
properties	String (JSON)	Yes	-	JSON object of properties to report. Uses merge-patch semantics — only the provided keys are updated. Example: {"firmwareVersion": "2.1.0", "status": "running"}
timeoutMs	Number	No	10000	Maximum time in milliseconds to wait for IoT Hub confirmation (1000-60000)

All function parameters support expression syntax ({{ expression }}) for dynamic values from the pipeline context.

Input

The node receives the output of the previous node as input. If the properties parameter is not explicitly set in the function configuration, the node passes the pipeline input directly as the reported properties. Use expressions like {{ $input.payload }} to pass dynamic data.

Output Structure

On success the node produces:

{
  "success": true,
  "functionId": "bcd123ef-4567-89ab-cdef-000000000001",
  "data": {
    "statusCode": 204,
    "bytesWritten": 89
  },
  "durationMs": 120,
  "timestamp": "2026-04-03T10:30:45Z"
}

Field	Type	Description
success	boolean	true when the twin update was accepted by Azure IoT Hub
functionId	string	ID of the executed function
data	object	Twin update result details (see below)
durationMs	number	Execution time in milliseconds
timestamp	string	ISO 8601 / RFC 3339 UTC timestamp

data fields:

Field	Type	Description
statusCode	number	HTTP-style status code from Azure IoT Hub. 204 indicates success (No Content).
bytesWritten	number	Size of the reported properties payload in bytes

Merge-Patch Semantics

Twin Report uses merge-patch semantics. Only the properties you provide are updated — existing reported properties that are not included in the payload remain unchanged. To remove a reported property, set its value to null:

{
  "oldProperty": null,
  "newProperty": "value"
}

Payload Size Limit

Azure IoT Hub enforces a maximum reported properties size of 32 KB. Payloads exceeding this limit will fail with a validation error.

Correlation and Timeout

The Twin Report operation uses a request-response correlation pattern over MQTT. A unique request ID is generated for each update, and the node waits for a correlated response from Azure IoT Hub. If no response is received within the configured timeout (default 10 seconds), the operation fails.

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Settings Tab

All Azure IoT Hub node types share the same Settings tab:

Setting	Type	Default	Description
Description	Text	-	Optional description displayed on the node
Timeout (seconds)	Number	Pipeline default	Maximum time the node may run before timing out
Retry on Timeout	Toggle	Pipeline default	Automatically retry the node if it times out
Retry on Fail	Toggle	Pipeline default	Automatically retry the node if it fails
On Error	Selection	Pipeline default	Error strategy: stop the pipeline, continue to the next node, or follow the error output path

When left at their defaults, these settings inherit from the pipeline-level execution configuration.

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Usage Examples

Forward OPC UA Readings to Azure IoT Hub

Scenario: Publish PLC temperature and pressure readings to Azure IoT Hub for cloud analytics.

Pipeline:

1. OPC UA Trigger — monitors temperature and pressure nodes
2. Set Node — formats the data as {"temperature": $trigger.payload.value, "timestamp": $trigger._metadata.sourceTimestamp}
3. Azure IoT Hub D2C Send — publishes formatted telemetry with routing property messageType: telemetry

Node Configuration:

• Connection: Factory IoT Hub
• Function: D2C Send with data expression {{ $input }}
• Routing Properties: messageType: telemetry, source: plc-01

Acknowledge Configuration Changes

Scenario: When a Twin Desired trigger updates the device set-point, apply the change and confirm via reported properties.

Pipeline:

1. Azure IoT Hub Twin Desired Trigger — detects desired property changes
2. PLC Write Node — applies the new set-point to equipment
3. Azure IoT Hub Twin Report — confirms the applied configuration

Node Configuration:

• Connection: Production IoT Hub
• Function: Twin Report with properties expression {{ {"targetTemperature": $trigger.payload.targetTemperature, "lastConfigUpdate": NOW()} }}

Periodic Device Health Reporting

Scenario: Report device health metrics to Azure IoT Hub on a schedule.

Pipeline:

1. Schedule Trigger — runs every 5 minutes
2. JavaScript Node — collects CPU, memory, and disk metrics
3. Azure IoT Hub Twin Report — reports {"health": {"cpu": ..., "memory": ..., "disk": ...}, "lastHealthCheck": ...}

Node Configuration:

• Connection: Device Management Hub
• Function: Twin Report with properties expression {{ $input }}
• Timeout Override: 15 seconds