AWS Tutorials - Understanding Device Shadow Service in AWS IoT Core
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- เผยแพร่เมื่อ 10 ก.ค. 2020
- The Workshop URL - aws-dojo.com/workshoplists/wo...
A device shadow is a JSON document that is used to store and retrieve device state information. The device shadow is associated with AWS IoT thing object. Any application or service which wants to know the device state; can access the device shadow irrespective whether the device is connected to AWS IoT or not. Shadow communications use request/response model using the publish/subscribe communication model of MQTT. Every shadow action consists of a request topic, a successful response topic (accepted), and an error response topic (rejected).
In this workshop, you perform update, get and delete actions on the device shadow document using MQTT based communication. You will use MQTT client as part of AWS IoT Service to complete the workshop. - วิทยาศาสตร์และเทคโนโลยี
I am literally searching for this. Thank u
great step by step explanation
Glad you liked it
Thanks very good explanation.
You are welcome!
Thank you 😀
You're welcome 😊
Thank you. Your video does a good job of explaining WHAT AWS IoT Shadows are for. I am confused at HOW it does it. If AWS IoT is using MQTT protocol then all nodes will Publish (send) data or Subscribe (be open to receiving) data. My understanding is that when a device reconnects after being disconnected it does not "request" anything. It is merely listening (Subscribed) to any messages Published to a particular topic. It would be the job of the MQTT Broker to retain a messages and transmit them when Subscribers registered for that topic are connected. Does AWS IoT work differently to standard MQTT? Can anyone answer please?
I would recommend to read this link - docs.aws.amazon.com/iot/latest/developerguide/iot-shadows-tutorial.html
So do IOT devices need to publish telemetry data to Shadown topics and not the actual topics ? can someone clear my doubt here. :(
if you just want to exchange messages and your devices are going to be online all the time, you can simply use MQTT based messaging using AWS IoT Topic.
But if your device can go offline, shadow is better way.
if you want to maintain state of the device, shadow is the way.
Hope it clarifies.
One question: Do we need to create separate things for each devices?
i.e i have 10 same kind of devices, then i need to create 10 thing or i can use in topic.
ideally - each device should be separately registered as thing and each should have their own certificate. Then each device also maintains its own shadow. But technically - you can register one thing with a certificate and all devices can use that certificate to send messages to one topic. Devices can send device id to identify their messages and their part of shadow. Sharing one device thing makes it more complicated to manage.
@@AWSTutorialsOnline
Please correct me if I am wrong, if each device publish and subscribe it's message by own "Topic". It means he will create 10 "Topics", then I think he can handle 10 device easily with one registered device on AWS IOT
The purpose of the device shadow is to maintain state of the each device individually. if you register just one device thing- then all the devices are sharing the same shadow by adding the device identity in the state details. Again technically possible but not manageable and will bring overhead. For instance, since all the devices are sharing a single device shadow, when a device updates its part of shadow / state, other devices will be notified about which is not required. Keep individual device things and their shadow makes the whole thing more manageable.
Dear sir can you make a video how to send and receive data from device shadow to Desktop based application i.e. C#
Sure I can create content for that. Just to be sure - you want to create a windows / web application using C# which can work with device shadow. Please confirm.
@@AWSTutorialsOnline Dear sir, Thanks for your reply. For Widows.
@@abeehahussain1920 Ok sure. I will make one soon,
Meanwhile - I uploaded a video about device defender couple of days back - let me know what you think. Also feel free to suggest for more topics.
I have watched this video, which is also very helpful for AWS IoT students,
Sure I will suggest some topics
Part_1: Connect raspberry pi/or any other micro controller with AWS iot and publish and subscribe data ( LED on off) to AWS iot
Part_2: then connect this AWS iot device (device shadow ) to windows application C# and send and receive data from that device shadow, (means create two buttons for LED ON and OFF and one text-box to display the the value of LED is on or off ).