I have two apps with same UISupportedExternalAccessoryProtocols. These are communicating with the MFI certified device. How I can know that the session is already created with other app on the same device. So I can alert to the user that you can't create multiple sessions with the same accessory at a time.
Please help to fix this. Thanks in advance.
I personally consider AyBayBay's answer invalid, since you tagged your question with the "iOS tag" and NSDistributedNotificationCenter is not supported on this platform. (There is a low level api to do this, but I think it's in a private framework)
If you are pretending to target your app to iOS8+, the simplest way to do it is using iOS8's AppExtensions feature. I made some tests creating a session within my app, and sending info to the device from another app using extensions the way below.
some app -> app extension -> my app connected with ext.device -> ext.device
so I'm pretty sure you can check if the session is opened or not and return this info to the caller app.
FYI: To pass info to another app you can also use URLSchemes or UIPasteboard too, but both behaviours in a different way than AppExtensions and I think it not fits on your case. Maybe it helps someone else...