Dart Device SDK for Azure IoT Hub

An unofficial, independently maintained pure-Dart device SDK for Azure IoT Hub, targeting native runtimes.

This project is not affiliated with, endorsed by, or supported by Microsoft.

Experimental prerelease: the public API may change. Behaviour follows the pinned stable C# device SDK; see the compatibility reference for source/test mappings and intentional differences.

Features

Implemented features are listed below. See testing for validation coverage and remaining gaps.

Feature	Details
MQTT 3.1.1 over TLS	Default transport, port 8883
MQTT over secure WebSockets	Explicit selection, port 443; no automatic fallback
SAS authentication	Shared key, supplied token or asynchronous token provider
X.509 authentication	Application-configured SecurityContext; WSS requires explicit TLS renegotiation opt-in
Device-to-cloud telemetry	QoS 1; application properties, message/correlation IDs, content type/encoding
Device twins	Read desired/reported properties, patch reported properties (including deletion with null), receive desired patches and restore subscriptions
Direct methods	Named/default async handlers, responses and subscription recovery
Cloud-to-device messages	Polling or callbacks, properties and explicit ordered completion
Retry and reconnect	Transient failures; bounded pending work, no offline persistence
Connection-status callbacks	Connection, recovery and shutdown notifications
Cancellation and timeouts	SDK-owned tokens; finite timeout across retries

File upload, module clients, IoT Plug and Play (model IDs/components), AMQP and HTTPS transports are not implemented.

Usage

Requires Dart 3.13.5 or later within Dart 3. Add the prerelease to your project:

dart pub add 'azure_iot_hub:^0.1.0-dev.1'

Import the package library. Connection strings should come from secure configuration:

import 'dart:convert';
import 'package:azure_iot_hub/azure_iot_hub.dart';

Future<void> sendTelemetry(String connectionString) async {
  final client = DeviceClient.fromConnectionString(connectionString);
  try {
    await client.sendEvent(
      .new(
        utf8.encode(jsonEncode({'temperature': 21.5})),
        contentType: 'application/json',
        contentEncoding: 'utf-8',
      ),
    );
  } finally {
    await client.close();
  }
}

Operations connect implicitly; open() is also available. Select transport: .webSocket for WSS on port 443. The runnable example reads AZURE_IOT_DEVICE_CONNECTION_STRING, sends telemetry and retrieves the twin:

dart run example/azure_iot_hub_example.dart

Authentication

DeviceClient.withTokenProvider accepts an asynchronous SAS provider. Tokens are cached and refreshed when a connection requests eligible credentials; renewal does not schedule disconnects. See the authentication contract.

For certificate authentication, use DeviceClient.withX509(hostName: ..., deviceId: ..., securityContext: context). Prepare the Dart SecurityContext with trusted server roots, the device certificate chain and its private key before construction. The application owns certificate loading and renewal. For WebSockets on port 443, select transport: .webSocket and explicitly set context.allowLegacyUnsafeRenegotiation = true on a dedicated IoT Hub context. The SDK never changes this setting; server certificate verification remains enabled. See the X.509 contract and live test setup.

Twins and incoming messages

getTwin() returns Twin with desired and reported maps under twin.properties. Reported-property updates are JSON patches; desired callbacks deliver patches for the application to reconcile. See twin operations.

Direct methods use named/default async handlers returning MethodResponse. Cloud-to-device messages support polling and callbacks; call complete(message) after processing, in receive order. See the direct-method example and C2D contract.

Timeouts and shutdown

Operations have a finite timeout, four minutes by default, covering retries and reconnect waits. Optional SDK-owned cancellation tokens cancel individual operations without stopping recovery. OperationFailure exposes reason, delivery and an optional twin response statusCode. DeliveryState.unknown means the operation may already have reached the hub, so retrying can duplicate its effects.

Connection-status callbacks report connection, recovery and shutdown. close() permanently shuts down the client. See the public API contract.

License

MIT, copyright 2026 Marek Cervinka. Portions adapted from Microsoft's Azure IoT C# SDK retain their original copyright and MIT licence.