I am trying to determine if there is a way in android to associate a specific link key with an already existing remote bluetooth device instance.
Essentially what I want to do is create a connection with a non-discoverable bluetooth device without going through the pairing or re-pairing procedure.
I am not able to establish the link key with the device in a standard pairing procedure because I am working with a custom proprietary pairing mechanism. I would prefer to accomplish this task without using native code, but if I have to then I will.
I needed to solve this problem myself. The crucial step was finding this code, which told me to add the android.bluetooth package to my project, and add the files IBluetooth.aidl and IBluetoothCallback.aidl (which you'll find at the link).
Once you instantiate the IBluetooth object, you have access to the BluetoothService class, and can use any of the methods in IBluetooth.aidl. The method I was interested in was
setPin(String address, byte[] pin)
The problem with using it is the other Bluetooth code expects the pairing dialog to have been called already, and keeps track of that in a HashMap in the BluetoothEventLoop class. If you try calling setPin() without having initiated a pairing request, you'll see an error like this:
setPin(<address>) called but no native data available, ignoring. Maybe the PasskeyAgent Request was cancelled by the remote device or by bluez.
So the workaround for me (using the Chat example) was starting the connect thread to initiate the pairing request, then sleeping 500 ms to ensure the thread had started, then calling setPin().
there is no public api mechanism to associate a link key with a device without going through the pairing process.
After pairing this association is automatically created (aka bonding) once devices are bonded then further connection will re-use the link key that was generated previously.
even if device is non-discoverable you should still be able to connect bond / pair with it, if you know the device bluetooth address.
internal / private mechanism by changing the underlying android bluez code, and hooking up to feed a pre-generated link key etc is theoretically possible and it will be a difficult project and a custom solution.
that is assuming that you have the link keys to feed / associate. note - link key is a function of the device address of both devices in addition to device clock etc.
bluetooth
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I would have to build two apps (Android and iOS) and control some equipment via Bluetooth. For clarification, i cannot just use OS device discovery to connect to the equipment because there's hundreds of them and their position is very important (as well as the user's position when issuing commands), thus it's less of a hassle for operators to just point the phone's camera at a QR code and connect than having to go through a long list of devices with mangled names.
I haven't found many details about specifically using a QR code for bluetooth connections, but i figured that people experienced with this kind of communication will be able to say if it can be done. Please correct me if i'm wrong, but my understanding is that a bluetooth socket is not that different from a TCP one and a connection could be established by knowing the server's credentials.
Can I use a QR code to store device credentials that I can use to establish a connection? It doesn't really matter how much information needs storing, the QR code can contain any sensitive information.
Is there anything more, apart from the UUID, that would need storing on the QR code?
Is it simpler to configure the device as a server and the phone as a client for this specific request? There will be multiple operators that will need to work with these devices.
This is specific to Android and iOS, but if the points above were possible, would I get an OS pop-up window for each connection? Would skipping the discovery step save the operator the hassle of having to confirm the connection to the OS?
If the target device is configured as a server, each with its UUID as the QR code, can i scan that code and open a socket to that very device without manually connecting to it from the phone's menu?
I'm developing an android BLE app in which i try to establish a stable Connection between the app and a BLE device.
To achieve this i want my app to keep the BLE device data in shared preferences or somewhere.
After app close, i'd like my app to retrive this data and attemp a connection without scan for devices.
I prefer to avoid scanning every time becouse scan gives me a lot of problems and it takes time.
How can do it? Is there a way to save BLE data?
You need to store the Bluetooth Device Address (AB:CD:EF:01:02:03) of the device in for example shared preferences or in a sqlite db. Then use https://developer.android.com/reference/android/bluetooth/BluetoothAdapter.html#getRemoteDevice(java.lang.String) when you later restart the app to retrieve a BluetoothDevice object. Once you have the BluetoothDevice object you can use the connectGatt method as usual.
There are some undocumented things you need to keep in mind however. Due to some horrible design flaws in Android's BLE API there is no way to tell it if you mean the given address is a Public Address or a Random Address. (You can read more about different address types at https://devzone.nordicsemi.com/question/43670/how-to-distinguish-between-random-and-public-gap-addresses/). The getRemoteDevice method should take an additional parameter "random address/public address" but it doesn't. Without the correct address type, the Bluetooth controller cannot connect to the device.
Android's BLE stack has some internal heuristics to "guess" if the address is public or random, but unfortunately that differs between Android versions and also if you use autoConnect=true or false. However if you have bonded the device (https://developer.android.com/reference/android/bluetooth/BluetoothDevice.html#createBond()) then it will store in its internal DB whether the given address is public or random. If the peripheral you want to connect to uses a random resolvable address it can handle that as well if you use bonding. Therefore I strongly suggest to use bonding.
If you don't use bonding you will need to scan before you connect to the device, since when you start a scan and a device is detected, Android's BLE stack will temporarily (until next restart of Bluetooth) remember the address type for an address.
I will continue on Emil's answer.
Thanks #Emil for the 'big picture'.
Google API is flawed and you can't use getRemoteDevice() because it only understand 48bit address and do not know about all BLE address types.
You can't use Bonding if the device is dumb (anyone would be able to bond to it).
So your only solution is a Bluetooth scan.
However, since Android6 (Marshmallow) the user has to give location permission to apps using Bluetooth scanning. If you don't permit, it won't work.
So if you buy a Bluetooth thermometer (or heart-rate monitor or whatever), you have to permit the app to access location of your phone (or tablet).
That's absurd!
#Emil call it a 'Google flaw'. You may also call it a 'Google machination'.
If I was a thermometer designer, I would add a push-button to accept bonding. It seems ridiculous because the button will only be used once.
[1]: https://www.polidea.com/blog/a-curious-relationship-android-ble-and-location/
I have two Android devices. One is acting as a server and the other as a client. The client connects to the server and requests a file - this is done in one thread on the client and one thread on the server so that both can continue doing what they want.
The client then attempts to connect to the server again to request another file. Right now I am getting a java.io.IOException: Device or resource busy when attempting to connect (socket.connect()). Is it because Bluetooth (on Android) only allows one channel between two devices? (if it were another device it would work but if it is the same it doesn't ?) Note that both attempts are made with the same service name and UUID.
Even if the error is specific to my code, I would like to know if this is the case or not.
System: android 2.2.1 communicating with the bluecove bluetooth library.
Definitely not with the same UUID(universally UNIQUE Identifier).
Reference for that was taken from here
Maybe with more than one. You can connect multiple devices in the Server/Client style, you can try to set one of the devices as a server and start several clients on the other. My first guess would be to start several client threads, but you might have to find a way to change the MAC address for each of them.
Here you can find another discussion about how to change your mac address, but only works in rooted devices. I can't find anything else for non rooted ones. No idea on how to do this programmatically but it might give you a start.
Here there is a discussion about connecting several clients at the same time in a server. I got there from this question. ( I think this might be your closest shot)
Here you have a discussion about peer-to-peer networks.
AFAIK, multiple connectivity is not possible in case of Bluetooth Connection. Bluetooth is Connectivity API is by default Synchronized so only one connection at a time is possible. So you can not perform multiple connections.
However it can be possible in another way like making one connection , performing 2 seconds operation on it and then creating another connection and performing 2 seconds operations like in normal multitasking operating system happens.
I am developing an application which connects devices over bluetooth and exchanges messages. It works fine for paired devices, but I would also like it to automatically pair devices that are not paired. Like for example it could store and use the same PIN for pairing requests, I just dont know how to manage this request programatically in my applciation, how to automatically set and send the PIN when you get a pairing request and how to initiate such a request with the predefined PIN code.
Any snippets or thoughts would be highly appreciated! :)
EDIT:
I know its risky, I am developing this app for emergency situations only where no other means but bluetooth is available. Also is there maybe a way of premature pairing with devices without even connecting to them? Like lets say there is a list of MAC Addresses of those devices and I can use them to generate a bond with that devices so that they appear paired on my device?
You can't do this. To do what you want to do would create a huge security risk. Think about it, my device just comes anywhere in bluetooth range of yours and now I can send you anything I want without you knowing? You can't really do this and I highly recommend not trying to subvert it.
Reflecting the setPin method allowed me to send the pin automatically to the other device. I had to implement it in a broadcast receiver that is listening for pairing requests. Although I cant get rid of the dialog it just stucks there on the screen and I dont know how to close it (programatically) and continue the bonding procedure since this dialog is called from inside connect() which is a blocking method. I am not giving up on it yet though :)
With Bluetooth version 2.1 and above there is a method of pairing called the 'just works' association model. This is the lowest security method of pairing and has no protection against man-in-the-middle attacks.
However, this will provide a secure, encrypted link without the need to exchange pin numbers or verify device ID.
The API on different platforms may differ but the underlying HCI messages require that you indicate that your device (or one of the devices) has the following IO capabilities:
No Keyboard, No Display.
As you might have guessed, this is a mode for very
simple devices that use Bluetooth, such as a speaker or headphones.
If you can find the API to configure that, then the 'just works' association mode of Secure Simple Pairing will be used for pairing.
The next step is to store the link keys e.g. bonding. Many devices e.g. mobile phones, will still create a dialogue box to the user to ask if they want to 'remember this device', as user authorisation is specified by the BT specifications... but that's another problem.
Here's the scenario:
I need to write an application for Android to create a RFCOMM socket to a PC with a Bluetooth dongle (I'm going to write the server too).
My requirement is that the user doesn't have to pair device manually.
Actually, with a big hack, I'm using the createInsecureRfcommSocket.
A little scenario: I've an Android application which exchanges information with a Linux box with a RFCOMM socket opened. I can manually set the PIN on the devices (hard coding it IS an option)
I'm looking for different roads:
Write a JNI wrapper
As has been done here by Max Kellermann, I can write a JNI layer to make all the pairing phase. This should be a good option, but there's a problem:
The NDK 4b does not provide libbluetooth libraries, so -lbluetooth fails, as well as the NDK v.3.
Options:
Find the NDK 1.5 (which includes lib bluetooth). After days of web search I've been not able to find out. Anyone has or knows where I can find it?
Compile libbluetooth for Android by myself and use them for -lbluetooth. No lucky there, I'm not able to build them. Any hint?
Use something exposed by the APIs
Any one know how can I use createRfcommSocketToServiceRecord and have the user not to manually pair the device? Is it possible? How should I write the server?
Something I do not know
Maybe (sure!) there is something I do not know. Maybe I can use something else? Not RFCOMM? SDP?
Maybe I can manually pair with the Android API?
I hope to have been clear enough, if not just ask. And again, as it's not the first time, I'm in your hands :)
Thanks for all the support guys!
At the end, I can say that you can't.
Even if you find a way, using wrappers, writing C modules and so on, android evolution will probably change the thing you're using.
And so, there's no option. Sadly.
Let's see how Android Bluetooth API will change in the future.
Yes we can create it Rfcomsocket and listen the socket without user concerns and also without pairing devices.
https://code.tutsplus.com/tutorials/create-a-bluetooth-scanner-with-androids-bluetooth-api--cms-24084
Follow this !!
The Android Bluetooth API is not finalized, and will change. Use at your own risk. This class implements an API to the Bluetooth RFCOMM layer. An RFCOMM socket is similar to a normal socket in that it takes an address and a port number. The difference is of course that the address is a Bluetooth-device address, and the port number is an RFCOMM channel. The API allows for the establishment of listening sockets via methods bind, listen, and accept, as well as for the making of outgoing connections with connect, connectAsync, and waitForAsyncConnect. After constructing a socket, you need to create it and then destroy it when you are done using it. Both create and accept return a FileDescriptor for the actual data. Alternatively, you may call getInputStream and getOutputStream to retrieve the respective streams without going through the FileDescriptor.