Hello,
I ask myself about how the BLYNK library manage the communication between hardware and server.
It’s important to understand the behavior of the project when the hardware lost connection.
Do we lost the hardware measurements/data or is there retries untill the connection is retreived?
On the other side, do we lost the server commands or is there retries untill the connection is retreived?
Thank you
No one knows?
…Or It’s not clear?
Yet it’s important to know how robust and reliable is the communication…
If you use decent hardware, communication is fine. What are you using?
Arduino + shield enc28j60.
I work on monitoring systems in my job, such as SNMP on which I can choose timeout time for a request, number of retries if request fails…
So I think there is same seups in the BLYNK library.
A pratical example: my system send a a mail if a event occurs on my hardware. What happens if my hardware is offline a while just before the event? The mail is sent as soon as the hardware goes online, or the mail is lost?
Assume the worst and that everything is lost but if you use sync all will be fine.
Perhaps study the libraries.
the question here is actually interesting.
sync recovers data from the server to the device.
But what if there’s data on the device that needs to be sent to the server, but the internet connection is down?
Does the blynk library handle more than one attempt automatically or this part left to us tinkerers? 
Any data collected in the interim would probably be lost… depending on the initial connection method, Blynk.begin() or Blynk.config()… in the former, the device will stop running the code until reconnect (generally automatic), so no data collected. In the latter, if coded so the the sketch keeps running (and keeps trying to reconnect), then unless it is somehow buffered in code, it too will simply spit out data to nothing, until point of reconnection.
The methods to look for connection status is covered here http://docs.blynk.cc/#blynk-firmware-connection-management
Thank you for help.
I tested today and the notifications and data are well lost if disconnection happens.
No matter the datas, but notifications are critical for my project.
I’m going to improve reliability by using connection management functions.
++
Allright, the project is now really reliable by using Blynk.connected() method.
Thank you all!