I was searching for my Bluetooth problem a few days but I did not find any useful solution. I would like reading advertising data more precisely manufacturing data from peripheral devices via ios application when it is in the background. In my case, the peripheral devices are Nordic nrf51822 chips and a central device is ios phone. I have successfully implemented the Bluetooth background mode and it works well on the ios device. The Event handler DiscoveredPeripheral is called when the new peripheral device is discovered. But the problem is that it is called only first-time the peripheral device becomes visible. If I turn off and on the peripheral device the DiscoverdPeripheral event is not called anymore. I know that this is ios restriction, but I do not know how can I handle this ios limitation. In the end, I would like that app in the background starts scanning for peripheral devices with specific UUID periodically, for example, every 10minutes. At this point, I would like to ask if this scenario is possible to implement in ios if so I appreciate for any help.
The Event handler DiscoveredPeripheral is called when the new peripheral device is discovered.
This isn't correct. It will only be called once per call to scanForPeripherals. When the device connects, you should stop scanning. When the device disconnects, which you should see as centralManager(_:didDisconnectPeripheral:error:), you can begin scanning again.
Even better, if you only want to reconnect to the same device, don't scan at all. Just call connect for that peripheral UUID. It will continue running while you're in the background and wake you up when the connect succeeds.
To push this further, implement Bluetooth State Restoration, which will allow you to automatically reconnect even after reboots.
Related
I trying to connect peripheral using UUID in the background, It's working only when i interact with advertising beacon first time at foreground then my app went background its working background and lock mode also if First time my app is away from advertising beacon i put my app at background then will come near to advertising beacon it's not working. in console, they came last peripheral not found as that error will come, my question is :
is this possible to scan or connect Bluetooth using UUID for the first time without the app opening?
i already tried that solutions also :
iOS BLE device paired while app is in background or killed or suspend
iOS: didDiscoverPeripheral not called in Background mode
didDiscoverPeripheral: not working sometimes on background
Not able to search my BLE Device which is providing service ID in scan Response iOS
Source file : https://drive.google.com/file/d/1uVR_kA3NsQUpM-LLgrGgXCeZK6PBO-A7/view?usp=sharing
Found this question a bit interesting, so went about studying CoreBluetooth.
As per the Core bluetooth programming guide
Although you can perform many Bluetooth-related tasks while your app is in the background, keep in mind that scanning for peripherals while your app is in the background operates differently than when your app is in the foreground. In particular, when your app is scanning for device while in the background:
The CBCentralManagerScanOptionAllowDuplicatesKey scan option key is ignored, and multiple discoveries of an advertising peripheral are coalesced into a single discovery event.
If all apps that are scanning for peripherals are in the background, the interval at which your central device scans for advertising packets increases. As a result, it may take longer to discover an advertising peripheral.
Now in your provided sample the background modes are correctly provided.
iOS looks for advertising packets only in background [Passive] mode and not the response packets
Searching further bought me to this link
ios- Scan and connect to BLE peripheral in background
You can check and see if this too is the case with you
I'm trying to achieve the following scenario:
Open the app and connect to a BLE Peripheral. Working
Send the app to the background and keep the connection alive. Working
Turn off the BLE Peripheral and the app is notified of the disconnection. Working
Turn on the BLE Peripheral and the app is notified of the disconnection. Working
Turn off again the BLE Peripheral. Working
Wait 2 days with the app in background and turn on the BLE Peripheral, but the app does nothing. NOT Working
How can I achieve this last step? iOS kills the background apps when needed, but is there a way of getting notified when a previously-connected peripheral is discovered? I read something about CB State Restoration but I don't really know if this will solve this situation.
Core Bluetooth state preservation / restoration is exactly what you want. If your app is suspended, it will start you app if a peripheral connects / disconnects or a notification arrives. It is however broken by design in the way that your app will stop being woken up if Bluetooth is restarted for any reason. Examples are Bluetooth crashes (happens every now and then), if the user toggles Bluetooth or flight mode, or if the phone is restarted.
I'm currently trying to develop a Background Bluetooth related app, and I'm having some trouble scanning in background.
I followed the entire Apple IOS Bluetooth Background tutorial, but I cant figure out why scanning doesn't work in background (my info.plist is correctly set up to manage BLE Background tasks, both central and peripheral).
What I've tested so far :
1 - When my two devices are in range and in foreground, scanning works well.
2 - When the peripheral is in background, and the central comes active in foreground, scanning also works, peripheral is well detected.
Here comes the troubles
3 - first I launch my peripheral device, and I put the app in the background. Then on the peripheral device, I power off the bluetooth, I launch the app, I put it in background, and I power on the bluetooth.
In my code, the -(void)centralManagerDidUpdateState:(CBCentralManager *)central calls the scan [centralmgr scanForPeripheralsWithServices:[NSArray arrayWithObject:servicesUUID] options:scanOptions];, function which works perfectly in the foreground. But nothing happened, the peripheral is never detected by the central.
4 - I launch the central, bluetooth activated, and I put it in background. Then I took my peripheral device, I went out of the bluetooth range (in the specific case I went to my supermarket to buy some beers to drown my sorrow), I launch it there -also bluetooth activated- I put it in background and I came back in the proximity of my peripheral. Once again nothing happened, the centrals did not detect the peripheral.
Furthermore, after the cases 3 and 4, if I just put the central on the foreground (the peripheral stays in background), detection restart, without doing anything else. As if the scan was successfully triggered in the case 4, but waiting the app to come active to actually start detecting other devices.
Does somebody have an idea on how to proceed/overcome the problem?
Thank you!
Ps: I appologize for my English, I'm a bit rusty
Hi for details you can see this answer
but the short answer is one of your Apps must be in Foreground to connect to each other
Either your central device or the peripheral
Reason: for central you an only scan with providing the service UUIDs of the peripheral
and in background a peripheral cannot adverise its UUIDs
so even they are there they just don't know of each others presence
Moreover some more notable things about background scanning are
you should be aware that advertising while your app is in the background operates differently than when your app is in the foreground. In particular, when your app is advertising while in the background:
The CBAdvertisementDataLocalNameKey advertisement key is ignored, and the local name of peripheral is not advertised.
All service UUIDs contained in the value of the CBAdvertisementDataServiceUUIDsKey advertisement key are placed in a special “overflow” area; they can be discovered only by an iOS device that is explicitly scanning for them.
If all apps that are advertising are in the background, the frequency at which your peripheral device sends advertising packets may decrease.
See Apple Docs
Is there any way to "wake-up" (relaunch) an iOS application (a background task actually, not to show the application) whenver a bluetooth device is connected?
For example, the iOS OS kills the application due to memory lack. Then a couple of hours later the user connects his bluetooth device. Can the iOS notify my application that the bluetooth device is connected and run a background task?
In Android I see that I can create a BroadcastReceiver that is registered for when a bluetooth device is connected. I need something equivalent to that for iOS.
If you have a pending connect for your BLE peripheral and you have specified BLE central background mode then yes, your app will be relaunched. You also need to implement state preservation and restoration as described in the Core Bluetooth programming guide in the event that your app is actually killed (not just in the background).
Note that in iOS a user cannot connect to a BLE peripheral directly - your app is responsible for identifying the target BLE peripheral and issuing the connect command. This is described in the programming guide.
I am trying to make an Application using iBeacon in which One device will work as beacon Broadcaster and another one as Receiver.I gone through the similar thing in Run iPhone as an iBeacon in the background but the solution that present there is not for API of iBeacon so i am asking this thing again.
I succeed in being notified on Detector Device(receiver) even the App is in Background or in Quit mode. but Whenever Broadcaster Device's App goes in Background it stops Broadcasting packets and become no more as beacon. When it comes back in Foreground it again works fine. So the issue is Broadcaster has to be always in Foreground to Act as Advertiser or Broadcaster.
Is there anyway to advertise/Broadcast packets of iBeacon's even when App is in background mode.
I have enabled capabilities "Location Update" and "Acts as a Bluetooth LE accessory" from xCode.
Unfortunately, it is simply not possible to advertise as an iBeacon in the background on iOS. For an explanation as to why, see here: Can we start iBeacon transmitter in background?
Apple doesn't authorize it, it would be a mean to track an user which is quite against Apple current policy to preserve users' privacy.
The capabilities "Acts as a Bluetooth LE accessory" is to enable your application to continue being used as a bluetooth device (with a connection) when the app go in background mode. Advertising isn't a connected usage of bluetooth and isn't concerned by this capabilities.