I am using AWS IoT core for communication between Esp8266 with the application. But I could not read the state of the device when it disconnected not gracefully . Any help is helpful. Sorry my English is not good.
Connect/Disconnect Events
AWS IoT publishes a message to the following MQTT topics when a client connects or disconnects:
Go to the AWS iot core and subcribe both topic and pass your clientID
$aws/events/presence/connected/: A client connected to the message broker.
$aws/events/presence/disconnected/: A client disconnected from the message broker.
other wise you can subcribe to this topic also
$aws/events/presence/connected/#
$aws/events/presence/disconnected/#
you get the status for disconnected and vice versa for connected
For details you can have a refrence https://docs.aws.amazon.com/iot/latest/developerguide/life-cycle-events.html
Related
I'm trying to send telemetry to a device in Azure Iot Central, with HTTP GET requests.
I have a legacy iot application, and I am trying to migrate it to Azure IoT Central, so for now I need to synchronize my ongoing Iot Data to Azure IoT Central.
One way I found to do it quickly was to use Logic Apps.
I have successfully created the Iot Central application and Logic Apps configuration, and I also found a way to get device information and update properties, but I'm not finding where to send telemetry data.
Is it possible to do with Logic Apps, or there is another way to send the telemetry?
Any hints will be very useful, thanks!
you should use the REST POST request to send a telemetry data to the IoT Central App.
The following is an example for device1:
Note, that the iothubhostname must be obtained from DPS service and also the Authorization header (sas token) is required.
and the following screen snippet shows the IoT Central App Dashboard:
How to susbcribe to a telemetry events using MQTT and using C code? (this is a microcontroller code)
I can send data to a specified topic but when I trying to subscribe to this topic I got error message
This is the message from the log
"mqttTopic": "/devices/my-device/events/my_telem_topic1",
This is the error message from the log
"message": "SUBSCRIBE: Failed to subscribe to topic: '/devices/my-device/events/my_telem_topic1'."
To add to what Kamal posted:
Part of the confusion here is that both MQTT and Pub/Sub (where IoT Core puts your device's telemetry events) are called "topics".
There are 4 MQTT topics for devices to work with (this is all on device side, not Cloud side):
/devices/<device-id>/commands
/devices/<device-id>/config
/devices/<device-id>/state
/devices/<device-id>/events
The first two are there for devices to subscribe to in order to get updates from the IoT Core Admin SDK, the latter two are topics for device to publish data to the Cloud.
In order for a device to subscribe to another device's telemetry, it would need to be able to subscribe to the Pub/Sub topic that's receiving telemetry from the other device. This won't be done as part of the MQTT implementation, but rather, you'd need to implement the Pub/Sub API on your device. This is going to require a separate authentication path as well, likely a service account key that you add to your GCP project, then download to your device. The links in Kamal's answer should get you started if you want to go down that route.
Depending on what you're doing however, as they say, you can probably process the incoming telemetry from one device in a Cloud Function or similar, then set a config for the device that wants to be responsive to that telemetry. That way, if the device is online, it'll get it right away, or if it's not online, it'll get it upon reconnecting to IoT Core.
Telemetry events sent to Cloud IoT are sent to a Cloud Pub/Sub topic that is configured when the device registry is created and are not intended to be retrieved via MQTT on devices. One could use any of the mechanisms available in Google Cloud to subscribe to these messages (Cloud Functions, Cloud Dataflow, or a custom-written subscriber). Commands can be received by devices via MQTT. The topic for a device's commands is /devices/{device-id}/commands/#. APIs are available to send commands to devices.
One would generally send telemetry events from devices, analyze them with one of the aforementioned Cloud products, and then possibly generate commands to devices based on the results of that analysis.
I am working on an iot device using google-cloud-iot-core, but i would like to have allow for 3rd party support, so i want to change the host name of the mqtt, how can it be done?
Thanks in advance
If you change that endpoint, then you're no longer talking to IoT Core. It's not configurable, as that's the endpoint to talk to the service.
You can setup your own MQTT server somewhere else (could do it in GCE or GKE with a custom container) and make the hostname whatever you want, and then setup your own broker to take the MQTT payloads and create Pub/Sub messages, or even to act as a forwarding proxy to IoT Core itself I suppose (although security and auth might get a bit odd).
Or you could even just go directly to Pub/Sub. It all just depends on your need.
As I mentioned, changing the hostname for IoT Core (the mqtt.googleapis.com) it means that you aren't using IoT Core any longer. There's no other way to access the communication broker piece of IoT Core to do the Pub/Sub message creation, etc. If you don't use the IoT Core endpoint (hostname) then you'd be on your own for creating the Pub/Sub messages from the IoT device data.
I'm working with a 6LowPan IPV6 network of connected devices (nodes) that forward their data to a border router which is connected to the internet. I'm trying to figure a way so that each node shows up in Watson IOT as a separate device. Is it possible to have more than one mqtt connection on the border router to the broker ?
Each device connects to Watson IoT platform using the a client ID in a format such as this: d:$org:$devicetype:$devicid so each device would be connected with it's own unique ID.
Have you configured your router as a gateway?
If you are using your router as a gateway then it would connect with a g: instead of a d: such as g:$org:$devicetype:$devicid
gateway can publish events from itself and on behalf of any device that is connected through the gateway.
Refer to documentation for more details.
OK, how do push notifications work?
I found a nice tutorial: http://lessons.runrev.com/m/4069/l/59312
I get the concept that the device needs to register with the server but does the app essentially hold an AJAX connection to server or does the server somehow plug into the mobile phone network... ?
There are three essential components when talking about push notifications:
Your server
The providers server
Your mobile device
Your server is the sender. It sends the push notification to the providers server, which in turn sends it to the device. Your device, therefore, is the receiver. (Concluding that you don't have to "plug into the mobile phone network", this is all done by your provider - Google in this case)
Within your mobile application you just register an eventhandler which is fired when you receive a push notification.
Google called this C2DM (Cloud to Device Messaging), now GCM (Google Cloud Messaging) - you can get an introduction inclusive of an architectural overview and demos here at android.com.
To answer your question I know:
Both push notifications services (Apple's and Microsoft's) are using a persistent IP connection for implementing their push notifications functionality.
I think Android works the same way (at least with Android Cloud to Device Messaging (C2DM)). "It uses an existing connection for Google services". http://en.wikipedia.org/wiki/Android_Cloud_to_Device_Messaging_Service
But the answer is closer to AJAX, except I assume it is a simple "http" connection to Google Messaging service from Android, and the OS gets an alert of a new message and relays it back to a program that registered on it to want notifications.