[IoT Central] Best way to send telemetry data from Flutter application

Julien KERN 25

Hi,

We plan to develop a Flutter application sending telemetry to a IoT Central application. This app should be compatible for Android and iOS.

I can see on the documentation that the Microsoft Azure IoT SDK does exist in C, C#, Java, JavaScript & Python (https://learn.microsoft.com/en-us/azure/iot-central/core/tutorial-connect-device?pivots=programming-language-python), which won't be compatible with a cross platform Flutter application.

It also seems that the IoT Central API does not provide a way to send telemetry data (https://learn.microsoft.com/en-us/rest/api/iotcentral/).

I was then thinking to build an Azure Function that uses the Microsoft Azure IoT SDK.

Is that a good approach ?
- If No, how would you achieve this goal ?
- If Yes, do you have some tips ?

Best regards.

Julien.

Roman Kiss 2,241 Reputation points

2023-05-13T08:10:48.4533333+00:00

Hi @Julien KERN ,

In the case of using an Azure Function for device provisioning to the Azure IoT Central App, have a look at my answer here, where is a detail implementation for this solution.

Thanks

Roman
Julien KERN 25 Reputation points

2023-05-15T07:21:03.2866667+00:00

Hi @Roman Kiss ,

Your solution seems really interesting ! Unfortunately I have the feeling that the "Event" endpoint for a device no longer exist : https://learn.microsoft.com/en-gb/rest/api/iotcentral/2022-07-31dataplane/devices

Does your solution still work with the current API, as I see your SO answer dates back to 2020 ?

Best regards.
Roman Kiss 2,241 Reputation points

2023-05-15T11:02:56.9466667+00:00

Hi @Julien KERN ,

The telemetry data can be sent to the underlying Azure IoT Hub of the Azure IoT Central App based on the REST POST request.

Have a look at also another generic solution based on the Azure Event Grid Pub/Sub eventing model in my SO answer here, where the telemetry event is pushed into the Azure IoT Central App based on its IoT Subscriber (device provisioning and post telemetry data), the following screen snippet shows an example of this solution:

Note, that the above solution is a generic and the telemetry data can be sent from any virtual plug-and-play iot device (source of the interest) to the destination resource (well-known IoT Central App) as a modelled data using a PUSH manner.

Thanks

Roman
Julien KERN 25 Reputation points

2023-05-15T12:18:36.91+00:00

@Roman Kiss ,

Thank you for your answer.

I was not aware of Azure IoT Hub and its synergies with Azure IoT Central.

@Sander van de Velde provided some solutions below, and I will try to work out the best one for my needs among yours and his. Your thoughts would be appreciated as well.

Julien.
Roman Kiss 2,241 Reputation points

2023-05-15T13:51:10.06+00:00
@Julien KERN ,

You mentioned two following options:

App -> Bridge -> IoT Central

App (MQTT) -> IoT Central

Note, that the first one is a one-way bridge to forward a telemetry data to the destination resource using a connection less protocol https.

The second option is giving to you a full capability of the IoT PnP Device with Azure IoT Central App included the IoT Central REST features.

Have a look at my article Azure IoT Central Tester designed for Android without using a Device SDK where the device (android phone) can be turned into the simulator of the Virtual IoT PnP device connected to the Azure IoT Central App directly via the MQTT protocol.

Thanks

Roman
LeelaRajeshSayana-MSFT 13,456 Reputation points

2023-05-17T13:29:35.4433333+00:00

Hi @Julien KERN Greetings! I am following up to see if you any of the proposed approaches worked for you. Please let us know if you have any additional questions or need further assistance.

If any of the responses helped, please do click Accept Answer and Yes for the answer provided. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.
Julien KERN 25 Reputation points

2023-05-22T12:43:46.4733333+00:00

@Roman Kiss Thank you very much, will definitely have a close look at your (very detailed, btw) blog post.

Could you tell me why using MQTT is not the most indicated way of doing so ? I mean, if I stick to the IoT Central documentation, I cannot find any reference to it. Maybe I am missing something ?

In the following link : https://learn.microsoft.com/en-gb/azure/iot/iot-mqtt-connect-to-iot-hub#using-the-mqtt-protocol-directly-as-a-device, what should I use as iotHub-hostname since I have a IoT Central application but not an IoT Hub (besides the one underlying, as told by @Sander van de Velde ) ?

Best regards
Sander van de Velde 28,236 Reputation points MVP

2023-05-22T15:33:43.8966667+00:00

Hello @Julien Kern,

the IoT Hub inside Azure IoT Central is not directly available. You need to provision your device first using the also internal Device Provisioning service.

To answer the other question regarding MQTT not being advertised that much, that is because you are responsible for much more than just communication. Think about possible throttling and reconnecting.

Azure IoT Central is the SaaS solution for Azure IoT, created to simplify the most common needs.

This way, using the Azure IoT Device SDKs is more in line with the level of knowledge of users.

It is possible to use MQTT (basically, that is what the SDKs use too) but it's just more uncommon.
Roman Kiss 2,241 Reputation points

2023-05-22T16:14:20.7566667+00:00
Hi @Julien KERN ,

In addition to Sander's comment, check out the following documents:

Azure IoT Central architecture

IoT Central device connectivity guide

Also, watch the incoming session Build IoT solution with MQTT in Azure Event Grid on the Build 2023 (May 23th).

Thanks

Roman

Accepted answer

Sander van de Velde 28,236 Reputation points MVP

2023-05-14T20:56:12.4366667+00:00

Hello Julien KERN,

it seems you want to send messages from one application to Azure IoT Central as if these messages are coming from multiple devices.

This pattern is already described here and a sample implementation is found on GitHub.

You can modify this 'bridge' to your own needs.

Each incoming message (of your own format) is transformed into a message to be sent to the IoT Central portal. The bridge checks if the device needs to be provisioned first based on the device id.

You are free to modify it as much as needed but the solution is quite straightforward.

More details based on The Things Network are seen here.

If the response helped, do "Accept Answer". If it doesn't work, please let us know the progress. All community members with similar issues will benefit by doing so. Your contribution is highly appreciated.
Please sign in to rate this answer.

2 people found this answer helpful.
Julien KERN 25 Reputation points

2023-05-15T07:13:44+00:00

Hello Sander,

Thank you for these resources.

Actually, the data do not come from another IoT ecosystem, but rather a single sensor. The user would collect this sensor's data for a given time, via the Flutter application.

The documentation you provided really focues on a bridge between Azure IoT Central and another IoT Cloud, but I have the feeling that could work with my case. Whare are you thoughts on this ?

Best regards.

Sander van de Velde 28,236 Reputation points MVP

2023-05-15T07:42:02.9333333+00:00

Hello Julien KERN,

yes, it's the devices that generate telemetry which have to be dropped off in IoT Central in some way.

If your app running on your devices is not able to connect to IoT Central directly (using an Azure IoT Device SDK or with plain MQTT communication) your app needs a 'bridge'.

The sample bridge is exposing an HTTPS endpoint and implements the heavy lifting regarding IoT Central access.

The examples are showing 3rd party cloud integration but that does not limit the use cases. Everything capable of doing HTTP requests can access this public endpoint.

You probably need to add some way of security for the Azure Function to prevent DDOS or spoofing though.

I'm not aware of what capabilities you have with Flutter. Perhaps these can communicate with some backend and that backend is capable to make the calls to the bridge. Or your Flutter app can communicate to the endpoint itself.

So these alternatives are identified:

app -> flutter backend?? -> bridge -> iot central app -> bridge -> iot central app (Azure IoT Device SDK??) -> iot central app (MQTT??) -> iot central

based on your experience and the platform capabilities, you can chose the one that works for you.

Julien KERN 25 Reputation points

2023-05-15T12:12:41.73+00:00

Sander,

Yes, I already created a Device Template representing this sensor. In the workflow, I was planning to register each sensor as a Device. The smartphone is just a medium in this scope.

The SDK cannot be used unfortunately, but can use MQTT or a REST endpoint.

I think it is best to avoid an intermediate backend that would surely be the weak point (in terms of performance and security).

So my options are :

App -> Bridge -> IoT Central

App (MQTT) -> IoT Central

What do you think of the @Roman Kiss answer ? In particular :

Is Azure IoT Hub a good idea to, in fine, act like a bridge ? Maybe it does offer more possibilities ?

I feel like Event Hub is not necessary in my case, do you agree ?

Thank you very much.

Julien

Sander van de Velde 28,236 Reputation points MVP

2023-05-15T13:54:08.3933333+00:00

Hello Julien KERN,

if you are familiar with programming again the MQTT client, you can try to program against IoT Central too.

Keep in mind the IoT Hub within IoT Central is not exposed directly. You need to program against the DPS of IoT Central first (by provisioning your device).

You probably need to expose the modelId using MQTT too. I have not tested this but it seems the modelID can be added in the connection:

$"{hostName}/{deviceId}/?api-version={apiversion_2020_09_30}&model-id={modelId}"; // note the older api version

The example post I added above describes sending messages with C# as an example. I'm not sure which language you use.

As an alternative to programming the client, the bridge can simplify the integration. There is no need to add EventGrid or IoT Hub next to it. It only adds more costs and complexity. If you can connect to the Azure Function directly, your message will be ingested as being sent by the device itself.

Again, it now depends on your programming skills: if you are confident with MQTT, go for the raw MQTT connection directly. Otherwise, the bridge can take away some hurdles.
Sign in to comment

2 additional answers

LeelaRajeshSayana-MSFT 13,456 Reputation points

2023-05-12T20:07:40.97+00:00

@Julien KERN Greetings! Welcome to Microsoft Q&A forum! Thank you for posting the question here. It is an interesting use case, and we haven't encountered this yet.

As you observed, there is no SDK compatible with Dart language that has been tested yet. The programming languages offered in the tutorial Create and connect a client application to your Azure IoT Central application also provide references to the Underlying GitHub repositories of the respective SDK. You can probably leverage the code samples and extrapolate the implementation to Dart. However, it is a complex and laborious task as there are lot of dependencies that needs to be resolved.

I would definitely recommend going with using an Azure function as it would be easier to implement. Please refer the related question How to generate custom telemetry string data for a simulated device sensor in IoT Central where a solution has been shared on how to send simulated Data to a device on IoT Central with a custom device Template.

Hope this helps. Please let us know if you have any additional questions in the comments below and we would be glad to help you further.

If the response helped, please do click Accept Answer and Yes. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.
Please sign in to rate this answer.
Julien KERN 25 Reputation points

2023-05-15T07:16:22.7233333+00:00

Hello LeelaRajeshSayana,

Thank you for your answer ! Happy that this solution could work.

I will see what comes froms the discussion with Sander before accepting an answer.

Best regards.
Sign in to comment
Dom 1,466 Reputation points Microsoft Employee

2023-05-15T10:38:01.19+00:00

Another option to consider:

The internal IoT Hub(s) in an IoT Central application support the MQTT protocol for client devices to send telemetry (for background see: https://learn.microsoft.com/azure/iot/iot-mqtt-connect-to-iot-hub).

A quick web search shows you can use MQTT from a Flutter app, for example: https://pub.dev/packages/mqtt_client
Please sign in to rate this answer.

0 comments No comments
Sign in to comment