Is it possible to be notified when a Bluetooth Device is connected or disconnected from iOS even when my app is in background ?
On Android, I use the ACTION_ACL_CONNECTED and ACTION_ACL_DISCONNECTED events. But I cannot find equivalents for iOS.
I found the CBCentralManager that can be used to monitor Bluetooth events, but my functions aren't called when a bluetooth device is connected/disconnected, only when I enable/disable the bluetooth. Is it an error on my side or is it normal ?
I also found the doc about Audio Route changes, that can also be an idea to detect the bluetooth connections/disconnections. Just check the kind of new route and detect the connected bluetooth devices at that time.
In the doc, I also found NSNotification types like IOBluetoothHostControllerXXX but nothing is explained about them. Did someone already used them ?
Is there something better or am I missing something ?
You cannot receive notifications about the connection and disconnection of Bluetooth peripherals generally. You can get connection and disconnection events for BLE peripherals that your app connects to.
For example, if your app initiates a connection to a heart rate sensor then you will get a call to your CBCentralManagerDelegate connection function when the connection succeeds. If that device subsequently is switched off or goes out of range then you will get a call to the disconnection delegate method.
If some other app initiates and makes the connection then you will not get a callback.
As you mentioned, you can monitor audio route changes to infer that a Bluetooth audio device has been connected/disconnected, but this will also fire when headphones are plugged in.
Related
I realise most of the searches are quite old on this topic and not after Core Bluetooth now supports more than just BLE connections (https://developer.apple.com/videos/play/wwdc2019/901?time=556).
Simply by running the RxBluetoothKit example app I am able to discover my speaker and inspect its services. However I am unsure how to actually get the speaker to pair with the phone, after a while the speaker disconnects. I am struggling to get information on the protocol and/or how to proceed.
Or is this still not possible: "And so if you're calling connect on a BR/EDR device, if your app is in foreground, then we'll try to make a connection out to that device for you." - it seems like querying and communication with an already paired device is what they were getting at in the talk.
Thanks in advance.
I've noticed that when you disconnect for a bluetooth device in an application the iOS device will continue to hold that connection for around 10 seconds. I've attempted to get around this by writing to a characteristic that causes the bluetooth module to cancel the connection with the iOS device instead but that isn't working (mostly because I changed the module and the iOS doesn't see the change because I assume the device is cached somewhere). Is there a way to make it disconnect instantly in code? I am using the swift command
manager.cancelPeripheralConnection(peripheral) currently.
Unfortunately, there isn't. The only way to tell the system to disconnect a peripheral is via the cancelPeripheralConnection method that you are already using. Yet, if you call this method it doesn't necessarily mean that the peripheral will be disconnect.
Background
On iOS the whole BLE connection management is maintained by the operating system. That means that no single application "owns" a connection. All BLE functionality is multiplexed to allow more than one application to gain access to centrals and peripherals.
For example, if you have installed a fitness application that tracks data from your heart rate sensor in the background then you can also "connect" to the heart rate sensor in your app but you will be unable to trigger a real disconnect as long as the fitness app maintains a connection.
The disconnect delay you have noticed is basically an optimization of the operating system. If no application holds a connection to the peripheral anymore it will wait for some time (to avoid unnecessary connect/disconnect cycles) and then trigger the disconnect on the bluetooth chip.
Hope that helps.
In iOS when you call the CBCentralManager method cancelPeripheralConnection(CBPeripheral), it does not always immediately terminate the connection. As Apple's documentation states:
Because other apps may still have a connection to the peripheral, canceling
a local connection does not guarantee that the underlying physical link is
immediately disconnected. From the app’s perspective, however, the
peripheral is considered disconnected, and the central manager object calls
the centralManager:didDisconnectPeripheral:error: method of its delegate
object.
If you have a need to immediately terminate a connection programmatically, say to free up the peripheral to be connected from another central device or to reset one's own security layer, then you need to follow the procedure described in the following StackOverflow thread:
iOS 6 - Bluetooth LE disconnect
which is for the app to send your own proprietary command to the peripheral that tells the peripheral to disconnect through normal means (e.g. "GAPRole_TerminateConnection" or "GAP_TerminateLinkReq" or "LL_Disconnect" or "HCI_Disconnect[_*]" with reason HCI_DISCONNECT_REMOTE_USER_TERM). This always works and is not delayed by the connection supervision timeout because it is a formal disconnection notifying the central device (i.e. iOS). The supervision timeout (up to 6 seconds in iOS; on Android the default is 20 seconds) only comes into play if the disconnection is unplanned as with going out of range or if the peripheral does a disconnect without notifying the remote device as with "LL_EXT_DisconnectImmed" (only available in some BLE peripheral implementations).
I am writing an iOS application which will communicate to a device using Bluetooth Low Energy (BLE).
When my connected device is out of range, my application is getting disconnect event.
But I am not getting any connect event when the device comes back to the range.
Please suggest any approach to detect when the device comes back to the range.
when you get the event that the device is no reachable anymore, you can launch a method which continuously checks if the device is still not reachable.
For example: while(isConnected==false)...
You say that you get a notification if the device disconnects, so you can use that event to launch such a method
When you receive the disconnect event, just restart the scan function:scanForPeripheralsWithServices or you can setup the scan mode to accept duplicate key by [_manager scanForPeripheralsWithServices:self.targetDeviceServiceIDs options:#{CBCentralManagerScanOptionAllowDuplicatesKey:#YES}]. which means the same device would be discovered for many time until you stop scanning.
Just reconnect in your disconnect method if the connection times out. There's no need to start a scan. It will automatically try to reconnect until it gets in range.
When your device get disconnected or goto out of range of Bluetooth then you don't need to scan for Peripheral devices because it already scanned for the BLE devices.
Call function [centralObj connectPeripheral:peripheral options:nil]; into didDisconnectPeripheral delegate method when BLE device disconnected.
I want to get notified whenever my iOS device is connected/disconnected to internet through my app. This is possible in android by using broadcast receiver. Is there any broadcast receiver like component in iOS through which I get notification for detecting change in internet connection?
I have searched through internet a lot but did not get any solutions.
You can refer to Reachability API. You might want to run this as a silent background thread and alert once there is a change in network connectivity.
I have worked on an app which read heart rate from server kinds of bluetooth low energy HRM(Heart Rate Monitor)by bluetooth notification.
And I have added the "App communicates using CoreBluetooth" into the app's "Background Modes".
It works fine when the app is in foreground, but when the app is in background, one of the Heart Rate Monitors is always to be disconnect with the app in sever minutes.
So I debugged the app and find that, this kind of HRM is always push notification irregularly.The interval between notifications is from 1 second to 20+ second.
I know that when the app is in background, iOS will stop the bluetooth connection if it is too long between bluetooth notifications.
So my question is: Is it possible to keep the connection when the app is in background?
Is reconnection the only way to solve my problem?
Detecting the disconnection and reconnecting to the peripheral will make your app more robust as it will handle the case where the peripheral goes out of range and then returns in addition to the case you are seeing.
When the peripheral is disconnected your centralManager:didDisconnectPeripheral method will be called on your delegate. In this method you can call connectPeripheral:options again to re-establish the connection. iOS will either do this immediately if the device is still in range or automatically later, once the device comes back into range.
Once your centralManager:didConnectPeripheral method is called you can re-establish the characteristic monitoring.
Edit Clarify that you can call connectPeripheral immediately