Most of time, this works normally in my application. Unfortunately, sometimes it never been triggered after discoverservice is called.
My code is:
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{
NSLog(#"Did connect to peripheral: %#", peripheral);
[self.delegate statusMessage:[NSString stringWithFormat:#"Did connect to peripheral: %#\n", peripheral]];
peripheral.Delegate = self;
NSArray *serviceArray = [NSArray arrayWithObject:_uuid_tpms_sensor_service];
[_peripheral discoverServices:serviceArray];
[peripheral discoverServices:serviceArray ];
}
Some posts relative with this are
CoreBluetooth never calls didDiscoverServices on iPhone5S
iOS CoreBluetooth not scanning for services in iPad Air
iPhone does not discover Services on a Bluetooth LE tag on reconnection
The final conclusion should be an issue in iOS. My question is that, given that it's iOS problem, how to work around this?
Many thanks to Larme and henrik as I got many ideas from your reply.
After three days verification, it seems I have find a work around for this problem (the problem is more likely a limitation of Bluetooth stack of iOS rather than an issue)
I'd like to summarize my findings and work around here:
[root cause]
Bluetooth stack in iOS is not robust enough, it's therefore the internal state machine become corrupted after some unexpected API calling.
As the BTLE radio follows a certain pattern where it interacts with one device connection query at a time, BLE application should follow the API sequence of connectperiperal-->discover-->read-->disconnect (trigger by local, peer device or supervision timeout on link layer).
Apple admitted that this was an issue in iOS.
[resolution]
follow the API calling sequence described in the above
Hope the summary is useful for other person.
Too many rogue app's not handling the BLE stack properly can cause it to crash. Then the phone needs to be restarted. iOS7 and 8 are much more robust than in the early life of iOS BLE.
Android are still less robust. Programmers forget to release resources or might try to write new data before the old has been transmitted.
This can happen a lot if you use X-code and you stop your app at a point before it releases resources etc. This can still crash iOS BLE stack.
Related
I know you can use this service to have devices like smart watches intercept notifications from iOS devices. But can you receive these iOS notifications on a Mac through OS X?
I want to be able to have my OS X program detect a specific notification type that is received in iOS. I tried browsing for the ANCS device on my Mac, but it didn't show up. I know you can't do this between iOS devices, so I was wondering if maybe the same was true between iOS and OS X or not?
Thanks!
It's definitely possible!
Here's what you need:
An app on your iOS device which imports CoreBluetooth and uses CBPeripheralManager to advertise a dummy service with some custom UUID (not the ANCS UUID, it won't work). This dummy service is required for your Mac to "see" the ANCS service.*
An app on your Mac which imports IOBluetooth, initiates a CBCentralManager object, and starts a scan. You can do this as so:
[self.centralManager scanForPeripheralsWithServices:#[[CBUUID UUIDWithString:YOUR_CUSTOM_SERVICE_UUID]] options:#{CBCentralManagerScanOptionSolicitedServiceUUIDsKey:#[[CBUUID UUIDWithString:ANCS_SERVICE_UUID]]];
Make sure you set yourself up as a delegate to CBCentralManager to receive the delegate callbacks.
When your Mac discovers your device in didDiscoverPeripheral, connect to it:
[self.centralManager connectPeripheral:peripheral options:nil];
1 very important thing to note here is you need to retain your peripheral to a property if you wish to connect to it, otherwise it will be dealloc'ed. See this answer for a more detailed discussion.
In didConnectPeripheral, you need to set yourself up as a delegate to the CBPeripheral you're connected to then start discovering services:
[peripheral discoverServices:nil];
(All the callbacks from this point onward are for CBPeripheral)
In didDiscoverServices, you should get a list of available services. Loop through them as so and discover each service's characteristics:
for (CBService *service in peripheral.services) {
if ([service.UUID isEqual:[CBUUID UUIDWithString:YOUR_CUSTOM_SERVICE_UUID]]) {
NSLog(#"Found your Custom Service");
}
if ([service.UUID isEqual:[CBUUID UUIDWithString:ANCS_UUID]]) {
NSLog(#"Found ANCS Service");
}
[peripheral discoverCharacteristics:nil forService:service];
}
In didDiscoverCharacteristicsForService, you want to look for 3 characteristics:
ANCS Notification Source: UUID 9FBF120D-6301-42D9-8C58-25E699A21DBD (notifiable)
ANCS Control Point: UUID 69D1D8F3-45E1-49A8-9821-9BBDFDAAD9D9 (writeable with response)
ANCS Data Source: UUID 22EAC6E9-24D6-4BB5-BE44-B36ACE7C7BFB (notifiable)
For those notifiable characteristics, subscribe to them for updates:
if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:ANCS_CHARACTERISTIC_UUID]]) {
[peripheral setNotifyValue:YES forCharacteristic:characteristic];
}
If you want to check if those characteristics are have started notifying, do a if(characteristic.isNotifying) in didUpdateNotificationStateForCharacteristic.
You will get the actual NSData updates in didUpdateValueForCharacteristic with characteristic.value. The important thing to note here is that you will get informed of notification events by the Notification Source characteristic, but these will not contain that much information. If you want your Mac to play a sound or flash some Hue lights or something like that for every iOS notification, this will suffice. However, for the actual notification details, it will need to come from the Data Source characteristic, but you need to request for them by making very specific calls to the Control Point characteristic. This is where it gets really complicated, and you'll be able to get more information in the official ANCS Specification document.
If you want a shortcut or a look at how others have done it, check out these Github repos:
jamiepinkham/BTLE_ANCS
KhaosT/ANCS-Mac
indragiek/INDANCSClient
Just be careful as you may find bugs in some of these implementations, mainly in the processing of data sent by the ANCS Data Source (I had to get creative with my own error handling).
*** Some may argue that you can use "Service Solicitation" to expose ANCS without having an app running on the iOS device and/or without advertising a dummy Service (see options parameter in Step 2), but I haven't had that much success with it so perhaps there's something I'm missing.
What I am trying to do
I am trying to connect my app to a Bluetooth LE device which needs to be paired.
Current behaviour
There is no problem without pairing the device and my iPhone application. I am able to connect, reconnect and read/write characteristics without any problem.
But, if the device need to be paired, I am only able to read/write characteristics the first time, right after the pairing popup confirmation. The next time, I discover and connect the app to my device, but I don't have the rights to read/write characteristics data because (I guess) I am not using the pairing information.
Finally...
After spending few hours searching around the web with no luck here are my questions :
How can I connect my app to a Bluetooth LE device from my iPhone app using the pairing data stored in my phone? Am I missing something?
Is it possible that it is not an IOS problem because if pairing data are present in the phone for the connecting device, it is automatically used?
Is there someone with experience with Bluetooth LE and IOS to help me?
Update 2013-10-27
I have discovered that you can't read a protected characteristic by pairing authentication right after that the characteristic has been discovered if a pairing exists (no confirmation popup). No problem with non-protected characteristic! I don't know exactly why is happening, but the behavior is that the IOS app never receive answers from the device.
So if the first reading is done after, it doesn't cause problem. Here is the code I am using to discover characteristics with the data reading in comment.
- (void) peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error;
{
NSArray *characteristics = [service characteristics];
CBCharacteristic *characteristic;
if (peripheral != servicePeripheral) {
NSLog(#"Wrong Peripheral.\n");
return ;
}
if (service != batteryService) {
NSLog(#"Wrong Service.\n");
return ;
}
if (error != nil) {
NSLog(#"Error %#\n", error);
return ;
}
for (characteristic in characteristics) {
NSLog(#"discovered characteristic %#", [characteristic UUID]);
if ([[characteristic UUID] isEqual:[CBUUID UUIDWithString:kBatteryCharacteristicUUIDString]]) { // Bat
NSLog(#"Discovered Bat Characteristic");
batteryCharacteristic = [characteristic retain];
//--> generate problem when pairing exists between IOS app and device
//[peripheral readValueForCharacteristic:batteryCharacteristic];
}
}
}
You don't have to do anything in your app for pairing management.
If your app runs in LE Central mode, and the peripheral sends an Insufficient Authentication error code in response to a read / write request, iOS will automatically pair with your device and will retry the request.
If you disconnect from the device, and later reconnect again, the peripheral needs to send the Insufficient Authentication error code again for the iPhone to restart encryption. Again, you don't have to do anything special in your app here.
If your app runs in LE Peripheral mode, things are a bit different. When you set up your GATT database, make sure to set correct flags for both the CBAttributePermissions and CBCharacteristicProperties. This will tell iOS that it should send the Insufficient Authentication error code itself, if it is not paired. It is then the responsibility of the central device to start the encryption process.
In the Bluetooth Accessory Design Guidelines for Apple Products, further restrictions are described.
Your accessory needs the capability to resolve private Bluetooth addresses. The iPhone will change its public Bluetooth address every now and then, and only paired devices will have the correct key to resolve that public address and recognize the iPhone.
"Section 3.9 Pairing" is also interesting.
Note that if you pair without man-in-the-middle (MITM) protection, your peripheral can use the resulting key to resolve the private Bluetooth address of the iPhone. However, you won't be able to encrypt the channel.
Pairing with MITM protection on iOS involves entering a PIN code that is displayed by the remote device. Out-of-band (OOB) pairing where you send pairing data over an external channel is not supported by iOS as far as I know (at least there's no public APIs to set OOB data).
Long story short: if you have only a "Pair" / "Cancel" pairing, you cannot encrypt the LE channel but only recognize the iPhone in future connections. The nice thing is that you can still recognize the iPhone even if you unpair it on the iPhone side, and even after restoring the iPhone firmware ;-).
Regarding LE encryption in general: it's not secure anyways (see http://eprint.iacr.org/2013/309).
I'm using the iOS 7 Multipeer framework in my app but I'm experiencing a problem with devices disconnecting. If I open the app in two devices: device A and device B the two devices connect to each other automatically. However, after several seconds device A disconnects from device B. i.e. At first the connection is like this:
A ---> B
A <--- B
After several seconds:
A ---> B
A B
Device A maintains it's connection but device B get's a MCSessionStateNotConnected.
This means that A can send data to B but B can't reply. I tried to get around this by checking if the device is connected and if it's not, re-initiating the connection using:
[browser invitePeer:peerID toSession:_session withContext:Nil timeout:10];
But the didChangeState callback just get's called with MCSessionStateNotConnected.
Strangely if I send app A to the background, then re-open it, B reconnects to it and the connection is maintained.
The Multipeer API (and documentation) seems a bit sparse so I was assuming that it would just work. In this situation how should I re-connect the device?
I was having the same problem, and it seems to have been related to my app browsing and advertising at the same time, and two invitations being sent/accepted. When I stopped doing this and let one peer defer to the other for invitations the devices stayed connected.
In my browser delegate I'm checking the hash value of the discovered peer's displayName and only sending an invitation if my peer has a higher hash value:
Edit
As pointed out by #Masa the hash value of an NSString will be different on 32 and 64 bit devices, so it's safer to use the compare: method on displayName.
- (void)browser:(MCNearbyServiceBrowser *)browser foundPeer:(MCPeerID *)peerID withDiscoveryInfo:(NSDictionary *)info {
NSLog(#"Browser found peer ID %#",peerID.displayName);
//displayName is created with [[NSUUID UUID] UUIDString]
BOOL shouldInvite = ([_myPeerID.displayName compare:peerID.displayName]==NSOrderedDescending);
if (shouldInvite){
[browser invitePeer:peerID toSession:_session withContext:nil timeout:1.0];
}
else {
NSLog(#"Not inviting");
}
}
As you say, the documentation is sparse so who knows what Apple really wants us to do, but I've experimented with both sending and accepting invitations using a single session, and also creating a new session for each invitation accepted/sent, but this particular way of doing things has given me the most success.
For anyone interested, I created MCSessionP2P, a demo app that illustrates the ad-hoc networking features of MCSession. The app both advertises itself on the local network and programmatically connects to available peers, establishing a peer-to-peer network. Hat tip to #ChrisH for his technique of comparing hash values for inviting peers.
I liked ChrisH's solution, which reveals the key insight that only one peer should connect to the other peer, not both. Mutual connection attempts results in mutual disconnection (though not that a single-sided connection actually is, counter-intuitively, a mutual connection in terms of status and communication, so that works fine).
However, I think a better approach than one peer inviting is for both peers to invite but only one peer to accept. I use this method now and it works great, because both peers have an opportunity to pass rich information to the other via the context parameter of the invitation, as opposed to having to rely on scant information available in the foundPeer delegate method.
Therefore, I recommend a solution like so:
- (void)browser:(MCNearbyServiceBrowser *)browser foundPeer:(MCPeerID *)peerID withDiscoveryInfo:(NSDictionary *)info
{
[self invitePeer:peerID];
}
- (void)advertiser:(MCNearbyServiceAdvertiser *)advertiser didReceiveInvitationFromPeer:(MCPeerID *)peerID withContext:(NSData *)context invitationHandler:(void (^)(BOOL accept, MCSession *session))invitationHandler
{
NSDictionary *hugePackageOfInformation = [NSKeyedUnarchiver unarchiveObjectWithData:context];
BOOL shouldAccept = ([hugePackageOfInformation.UUID.UUIDString compare:self.user.UUID.UUIDString] == NSOrderedDescending);
invitationHandler(shouldAccept && ![self isPeerConnected:peerID], [self openSession]);
}
I have the same issue when devices trying to connect to each other at the same time and I don't know how to find a reason because we don't have any errors with MCSessionStateNotConnected.
We can use some crafty way to solve this issue:
Put into txt records ( discovery info ) a time [[NSDate date] timeIntervalSince1970] when app started. Who started first - send invitation to others.
But I think it's not a right way ( if apps start at the same time, unlikely... :) ). We need to figure out the reason.
This is the result of a bug, which I've reported to Apple. I've explained how to fix it in my response to another question: Why does my MCSession peer disconnect randomly?
I have not flagged these questions for merging, because while the underlying bug and solution are the same, the two questions describe different problems.
Save the hash of the peer B. Using a timer check the state of the connection continuously if is not connected try to reconnect with each given period of time.
According to apple document Choosing an inviter when using Multipeer Connectivity
“In iOS 7, sending simultaneous invites can cause both invites to fail, leaving both peers unable to communicate with each other.”
But iOS 8 has fixed it.
It seems that the .notConnected message is a false positive in that the device is still receiving data. So, I manually updated local connection state to .connected
It was hard to factor out other state from other examples. So, I wrote a bare bones MCSession example for SwiftUI, here: MultiPeer
I have an app that simulates heart rate monitor peripheral (The peripheral app).
I also have an app that receives the data and present it (The central app).
The central app decided to connect to the discovered peripheral based on its name.
The problem is that both app work perfectly good, except that the name is always "iPhone".
The advertising is done this way:
- (IBAction)switchChanged:(id)sender
{
if (self.advertisingSwitch.on) {
NSDictionary *advData =
#{CBAdvertisementDataLocalNameKey:#"Custom Name",
CBAdvertisementDataServiceUUIDsKey:#[[CBUUID UUIDWithString:#"180D"]]};
[self.peripheralManager startAdvertising:advData];
NSLog(#"Advertising");
}
else {
[self.peripheralManager stopAdvertising];
[[self timerInterval] invalidate];
NSLog(#"Stopped advertising");
}
}
But on the central side, inside
- (void) centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)aPeripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI
The name property never changed.
Is there anything that should be done?
What I have observed with CBPeripheral.name is that the device will, in fact, set the name to the name you select with CBAdvertisementDataLocalNameKey. This name is not persistent, though. If you disconnect the master and reconnect,the name will generally have been switched to "iPhone". If the peripheral disconnects due to an error, I have seen it reconnect with the correct peripheral name, but a new UUID.
There may be other situations where the name also switches to iPhone.
This appears to be a bug in iOS. I'm looking for confirmation before reporting it.
CBAdvertisementDataLocalNameKey only change kCBAdvDataLocalName in advertisementData.
When you nslog advertisementData, you will see some data like this:
{
kCBAdvDataIsConnectable = 1;
kCBAdvDataLocalName = Custom Name;
kCBAdvDataServiceUUIDs = (
"FB694B90-F49E-4597-8306-171BBA78F846"
);
}
Unfortunately, there is no other way to set the peripheral name. iPhone will always have the name: iPhone.
The advertisement is probably correctly seen on the central side. You may check by NSLogging the advertisementData. However, if you rely on the peripheral.name property, then that will either be empty (if you connect first) or contain the "iPhone" string.
I remember it is used to happen to me and I figured it was something to do with the way Core Bluetooth handles caching and service discovery. What Happened to me was that at first I received a default name like iPhone, iPad or nothing at all. But then after discovering services or trying to establish a connection the key magically changes to the value I had set on the other end.
Moreover, it seems it only happens the first time, afterwards, even between launches and subsequent runs of the app Core Bluetooth will try its best to return those values to you on the advertisement stage even on first discovery, but those might as well be outdated values.
my current implementation looks as follows:
NSString * baconName = [[UIDevice currentDevice] name];
NSDictionary *advertisementData = #{CBAdvertisementDataServiceUUIDsKey:#[[CBUUIDUUIDWithString:BACON_SERVICE_UUID]],
CBAdvertisementDataLocalNameKey:baconName};
And It just works for me, iPhones love Bacon, everybody does ;).
Hence, the best way to ensure you get any data you want, is to create another characteristic to transmit your flag and do constant discoveries of services and characteristics for Peripherals you are discovering, and accordingly minimise the discovery of existing or cached peripherals by caching or keeping a reference to them, CB is supposed to do this for ya, and they do their best effort but only you know the business logic of your app and what is important to you. I am overly paranoid and keep references to the discovered peripherals I am interested all the time. That is just me: it ensures I have the right information, and that I minimise scanning and constant re discovery of services and characteristics.
I Hope this helps.
In most such applications instead of identifying the peripheral by name, the client app should be identifying it by a service ID, and the server (peripheral), should be providing a either a standard service ID, as defined at bluetooth.org, or a proprietary service ID/name.
I have the same problem. I argee with Mike, this really seems like bug in IOS. If you discover your peripheral with TI multitool (for example) first, then your device will be discovered as you setuped in CBAdvertisementDataLocalNameKey.
to Dan1one:
you should use [[UIDevice currentDevice] model], not name, to get the string same to default.
I have made an iOS multiplayer GameCenter game, but right before publishing found an issue I don't know how to solve. In coding process I used Ray Wenderlich tutorial http://www.raywenderlich.com/3276/how-to-make-a-simple-multiplayer-game-with-game-center-tutorial-part-12
GameCenter view controller is shown, connection creates and game can be played until both devices are on the same Wifi network.
If I turn off Wifi on my phone and use 3G network, then try to start new game - in that case connection isn't made anymore. Both devices find each other, but hangs on "Connecting..." screen. It looks like that
- (void)match:(GKMatch *)theMatch player:(NSString *)playerID didChangeState:(GKPlayerConnectionState)state
is not called. Any ideas how to solve it or at least understand, where exactly is the problem?
I think that in your particular case the problem is that your 3G ISP restricts connections from necessary ports. The Apple docs say:
To use Game Center ... port forwarding must be enabled for ports 443 (TCP), 3478-3497 (UDP), 4398 (UDP), 5223 (TCP), 16384-16387 (UDP), and 16393-16472 (UDP)
I faced this issue too when trying to play on iPad connected via bluetooth to iPhone: there was "Connecting..." screen on each device.
But when I use built-in iPad 3G (with a different tariff plan) everything goes fine.
Just remind, in a normal match-making scenario match:player:didChangeState: may not be called. You should also check match.expectedPlayerCount:
- (void)matchmakerViewController:(GKMatchmakerViewController *)viewController didFindMatch:(GKMatch *)theMatch {
//...
if (theMatch.expectedPlayerCount == 0) {
NSLog(#"Ready to start match!");
}
}
Also I expected a similar problem with "Connecting..." screen, but on Wifi network.
And it was reproduced only on iOS6 and after I tried rematch via -[GKMatch rematchWithCompletionHandler:^(GKMatch *match, NSError *error) {}] before.
One device hanged on "Connecting..." screen but on the other matchmakerViewController:didFindMatch: was successfully called, but what is interesting is that match.expectedPlayerCount was 0 and match.playerIDs array was empty at the same time.
I think such error occurred because I tried to find a new match while previous match tried to reconnect on background thread in the same time. And because of that new match was obtained corrupted.
The decision is to wait for rematchCompletion being called and only then try to find new match. There is no interface in GKMatch to cancel rematch, so I use [[GKMatchmaker sharedMatchmaker] cancel] and after several seconds rematchCompletion is called with error and we are ready to start finding new match.
Also I figured out that old unsued GKMatch instances are not deallocated and continue to live somewhere in GameKit framework. And they may probably cause problems if the work with them is not finished correctly (i.e. not disconnected, or rematch is not canceled in my case ). So do not forget to call -[GKMatch disconnect] and finish any other kind of work before removing the last strong reference to the match object .