Hi Microsoft admin, i want to ask some questions about direct method of IoT hub. I am now developing a control application, write in Nodejs. I am successfully use the direct method, and i wonder if i can remove the response every time a direct method send from iot hub to device . I read document about direct method its say a full direct method operator take 2 message (request msd and respone msg). In my application, i just need the request (cloud-2-device) but not respone (device-2-cloud). My app need low latency so i choose this method. I wonder are there any methods suitable for this project ? , one way sending with lowest latency. Thank for your support

Instead of using a Direct Method, you can use a Cloud to Device (C2D) message instead. They don't require the device to send a response. The C2D message is designed for one-way traffic to your device, check out the table on this page on why you should consider C2D. It will have similar latency to a Direct Method.

Azure Iot Hub direct method send with out respone

Accepted answer

Matthijs van der Veer 4,376 Reputation points MVP

2020-12-01T19:38:39.583+00:00

Instead of using a Direct Method, you can use a Cloud to Device (C2D) message instead. They don't require the device to send a response. The C2D message is designed for one-way traffic to your device, check out the table on this page on why you should consider C2D. It will have similar latency to a Direct Method.
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3 people found this answer helpful.
long dao thanh 81 Reputation points

2020-12-01T19:50:36.127+00:00

Thank for your quick response. I will try the c2d message method and test if it is right for my project.
I also have one question about azure iot hub, to check the connection between iot hub and device, is there any way to do it with out send d2c msg or c2d msg to check they are successfully connected. For example programming with nodejs, is the nodejs sdk provide any function to do it. I have read document about order connection and use cosmosdb to store the connection msg, is this sample also use the msg to check?
Thank for your support. Wish you have a good day

Matthijs van der Veer 4,376 Reputation points MVP

2020-12-01T20:06:04.63+00:00

Do you want to check for a connection from the device side, or from the cloud side?

long dao thanh 81 Reputation points

2020-12-01T20:26:03.427+00:00

Hi, i want to check from the cloud side, i write a web app to control a iot device run 24/7 to send sensor value to cloud and receive command from web app, user can use web app to control the iot device at any time. So i want to make sure during the user control a iot device through web app, the connection between them always stable. If they lost connect, i will prevent the user to send new command
My plan is connect the iot device with iot hub whenever the user choose that device and hit the connect button. My project use a lot of device at the same time, but when control only one is connected, i think by doing that, it will not raise high latency. That is my plan so far. So i wonder is the nodejs sdk provide any function to check the connection or any method i can use
Thank for your support. Regards
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Azure Iot Hub direct method send with out respone

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