SDK?? You mean a Blynk.virtualWrite() command? If so, it technically gets sent to the Server and then to the App, so even if the App is offline at the time, when it starts again I think it should grab the latest values sent to all it’s widgets.
I suppose you could set up an eventor response… but depending on exactly what you are trying to do, I think Blynk will prevent anything that can cause a cyclic repetition…
Did you get it?
Yes I did.
Are you sure…how about now?
Yes, totally got it… see here…
Fine, but that was then, how about now?
You could also setup a sync every time the App comes online… but again, may be redundant.
As @Gunner said, you’re not sending the data to the app, you’re sending it to the server (either cloud or local). Provided the app is online, it’ll be displaying the data from the server, or doing the ‘juggling balls’ icon, or saying that the app is currently offline.
If you want to confirm that the data on the server is the same as the data you’ve just sent then simply read it back to the ESP32 and compare the result to what was sent.
If it’s more a case of wanting to acknowledge that an important piece of data has been seen by the user of the app, sort of like a ‘read receipt’ on an email, then maybe use a button to confirm that. Being more specific about exactly how you’d do that is difficult without more information about exactly what you’re to achieve, and why.
So look at that link i already provided… see the corresponding BLYNK_APP_DISCONNECTED() command… and figure out how to set up for flag so that a notification either doesn’t go out when the App is offline (if that matters), or trust the server to pass on the info later when the App is back (it seems to do that for me)… you have many options availed… have you tried any?
Not sure exactly what you are looking to do… but have you checked out the Table Widget?