# LoRaWAN Downlink Confirmed Data

**URL:** <https://discourse.nodered.org/t/lorawan-downlink-confirmed-data/51918>\
**Category:** General\
**Tags:** node-red-dashboard\
**Created:** [6 October 2021 11:18 UTC](https://discourse.nodered.org/t/lorawan-downlink-confirmed-data/51918 "2021-10-06T11:18:52Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Ryoyo123](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ryoyo123/32/49071_2.png) [@Ryoyo123](https://discourse.nodered.org/u/Ryoyo123)\
**Post date:** [6 October 2021 11:18 UTC](https://discourse.nodered.org/t/lorawan-downlink-confirmed-data/51918/1 "2021-10-06T11:18:52Z")

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I have a question about how to change the header of a LoRaWAN packet.

The upper 3 bits of "MHDR" in the packet header indicate the message type. If bit # 7, 6, 5 is set to "101", it will be "Downlink Confirmed Data".

I want to change the upper 3 bits of "MHDR" to "101" when sending downlink data via the route of MQTT-\> Network server-\> Gateway. How should I do?  
Could you give me some advice?

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**Author:** ![iiLaw](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/iilaw/32/14782_2.png) [@iiLaw](https://discourse.nodered.org/u/iiLaw)\
**Post date:** [6 October 2021 11:54 UTC](https://discourse.nodered.org/t/lorawan-downlink-confirmed-data/51918/2 "2021-10-06T11:54:48Z")

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Well this is Not the place for this question which is a deep #LoRaWAN protocol question.  
Let's take a step back  
Which LNS (LoRaWAN network server) are you using?

Normally the you would specify a confirmed msg via API  
Changing the MHDR should mean you need to re-calculate the MIC.

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**Author:** ![Ryoyo123](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ryoyo123/32/49071_2.png) [@Ryoyo123](https://discourse.nodered.org/u/Ryoyo123)\
**Post date:** [6 October 2021 12:29 UTC](https://discourse.nodered.org/t/lorawan-downlink-confirmed-data/51918/3 "2021-10-06T12:29:53Z")

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Hi iiLaw-san,

Thank you for your advice.

I'm using open-source LoRaWAN Server.

> **[GitHub - gotthardp/lorawan-server: Compact server for private LoRaWAN networks](https://github.com/gotthardp/lorawan-server)**
>
> Compact server for private LoRaWAN networks. Contribute to gotthardp/lorawan-server development by creating an account on GitHub.

Best regards

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**Author:** ![iiLaw](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/iilaw/32/14782_2.png) [@iiLaw](https://discourse.nodered.org/u/iiLaw)\
**Post date:** [7 October 2021 12:09 UTC](https://discourse.nodered.org/t/lorawan-downlink-confirmed-data/51918/4 "2021-10-07T12:09:14Z")

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ok I had a look there doesn't seem to be an API example of a downlink.  
Any reason you didn't look at at chirpstack this is a very widely used OS LNS stack and runs on constrained devices and server. Many LoRaWAN manufactures and network operators use it.

Sending a confirmed downlink is easy  
[https://www.chirpstack.io/application-server/integrations/mqtt/#scheduling-a-downlink](https://www.chirpstack.io/application-server/integrations/mqtt/#scheduling-a-downlink)

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [6 December 2021 12:09 UTC](https://discourse.nodered.org/t/lorawan-downlink-confirmed-data/51918/5 "2021-12-06T12:09:16Z")

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