I'm having a hard time understanding why a Bluetooth connection is able to be made without either pairing or trusting a device. I'm using bluetoothctl and and can connect two devices without pairing them first by using "Scan on" on the central side and "Advertise on" on the peripheral side.
could someone explain why this is happening?
Related
I'm trying to establish a connection between my PC running Ubuntu and my iPhone via Bluetooth automatically when it becomes available, after being manually paired beforehand. I've seen this to be possible with certain peripherals, mainly audio. For example, my phone will automatically connect to a Bluetooth speaker when it is turned on and Bluetooth is active on my phone; another example is my phone automatically connects to my car's radio system via Bluetooth when I turn the car on.
I'm not able to connect my phone to my PC without first initiating the connection from the smartphone's Bluetooth menu. I'm thinking that I could possibly write an application for the PC to attempt to connect to the device every few minutes or something, but it seems that the phone needs to be the device to initiate the connection.
The only information that I need for what I'm trying to do ultimately is that the devices can pair successfully. Essentially I'm trying to build a sort of proximity trigger between my phone and my PC without using Wi-Fi and GPS - I can't use these for some specific reasons.
Is there any way to make this happen?
Yes this should be doable as long as you use the Background Processing feature for iOS apps. In the example I'll give below, we'll have the PC be the peripheral and the phone be the central, but you can really have it working either way. You will need to do the following:-
First initial connection needs to be performed in the foreground (this is due to iOS's background limitations).
On the iOS side, you need an application that acts as a central that scans and connects to the remove device (check this example as a starting point).
Upon connection, you need to bond with the PC. Bonding is important as it will prevent you from having to do the pairing again in the future. However, pairing/bonding is managed by the iPhone's OS so you cannot write it in your application, so the workaround is to have an encrypted characteristic on the PC side that will force the iPhone to bond (this is covered later).
On the PC side, you need to have a BlueZ script that acts as a peripheral that is always advertising. You can do this using bluetoothctl (check the examples here and here).
Before you start advertising, you need to have a GATT server on the PC side (to do this, check this example).
When registering characteristics, ensure that one of them has the encrypt-read property (you can find a full list of the properties here).
Now when you attempt to read this characteristic from the iOS side, the two devices should bond (make sure that your PC is bondable which you can do this via these commands).
Once the devices are paired, your iOS app needs to be working in the background constantly scanning and attempting to connect to the same peripheral (have a look at this and this example).
You can find more useful information at the links below:-
Getting started with Bluetooth Low Energy
The Ultimate Guide to CoreBluetooth Development
How to manage Bluetooth devices on Linux using bluetoothctl
I have an android app that connects to a few classic Bluetooth and BLE devices. Starting from one of the security patch releases of Android 10 I am getting pairing requests on my Android device. Is there a way to automatically accept these requests in code? The BLE devices do not have a pin and only need a certain flow of read and write operations to pair. Right now my write operations are failing unless I wait for the bond state to change to BONDED which happens on accepting the pairing request on the Android device.
So far I've tried setPairingConfirmation(true) which does not seem to be working.
I guess the idea of pairing is that the user must accept that an "unknown" device being paired to his system. Otherwise different shady apps could just pair devices in the background without the user's consent.
A peripheral that is not meant to be paired to a user should hence not require pairing in the first place, to perform various operations.
I got an issue with reconnection to my BLE device.
Senario that works
- BLE Device is not paired
- Pi boots and start my App, find's the BLE device, pair and connect, receiving data
- Boot Pi and start my App, it will not pair as its already paired, it connects fine and receiving data.
Senario that does not work
- BLE Device is not pair or pair, does not matter
- If my BLE device disconnect due to power loss or out of range and gets powered up or back in range the Pi will reconnect and throw:
'System.Exception' in mscorlib.ni.dll
There is no user session key for the specified logon session. (Exception from HRESULT: 0x80070572)
If I try to reboot the Pi, the same message is thrown when I try to execute: await _readCharacteristic.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.Notify);
The only thing that works is if I unpair the device every time it disconnect.
This is the same issue that this guy has: https://social.msdn.microsoft.com/Forums/sqlserver/en-US/b98d77f2-bf5e-45fc-9495-1c444b54450e/uwpreconnecting-to-a-ble-csac-device-causes-exception?forum=wpdevelop
Maybe there is anyone here that has seen the same issue and solved it ?
Thanks
The reason for this particular error you are receiving is almost certainly that the BLE device itself is not storing the bonding information that is negotiated during the pairing process. For an existing BLE pairing to be re-used, the device must retain the bonding with its partner for future communication sessions.
Developers can sometimes work around this device shortcoming in their (non-Windows) PC or phone application by having the PC or Mobile app delete any previous pairings with the device already retained, and negotiate a new pairing each time it sees the Bluetooth device. This is possible because many Bluetooth devices have a static PIN, require no interaction for pairing, and remain in open pairing mode. So the app creates a new device pairing upon each communication. The Mac BLE API requires no user interaction for pairing and un-pairing as well.
But this solution is unworkable under Windows BLE API, because unlike regular Bluetooth, the Bluetooth Low Energy API requires user interaction during both the pairing, and un-pairing "ceremonies". The user must agree to every pairing, and must agree to every un-pairing. This makes this workaround solution a non-starter from a UX standpoint on Windows. My guess is the BLE device manufacturer isn't storing the bonding.
We ran into such a situation ourselves developing our own BLE driver to speak with our own BLE board; we had to re-do the firmware running our BLE device because while it would work under Mac OS and Android with the method described above, the BLE API available on the Microsoft UWP requires user interaction during the pairing ceremony. This seems the right way to do things, anyway.
I got an issue with reconnection to my BLE device.
Senario that works
- BLE Device is not paired
- Pi boots and start my App, find's the BLE device, pair and connect, receiving data
- Boot Pi and start my App, it will not pair as its already paired, it connects fine and receiving data.
Senario that does not work
- BLE Device is not pair or pair, does not matter
- If my BLE device disconnect due to power loss or out of range and gets powered up or back in range the Pi will reconnect and throw:
'System.Exception' in mscorlib.ni.dll
There is no user session key for the specified logon session. (Exception from HRESULT: 0x80070572)
If I try to reboot the Pi, the same message is thrown when I try to execute: await _readCharacteristic.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue.Notify);
The only thing that works is if I unpair the device every time it disconnect.
This is the same issue that this guy has: https://social.msdn.microsoft.com/Forums/sqlserver/en-US/b98d77f2-bf5e-45fc-9495-1c444b54450e/uwpreconnecting-to-a-ble-csac-device-causes-exception?forum=wpdevelop
Maybe there is anyone here that has seen the same issue and solved it ?
Thanks
The reason for this particular error you are receiving is almost certainly that the BLE device itself is not storing the bonding information that is negotiated during the pairing process. For an existing BLE pairing to be re-used, the device must retain the bonding with its partner for future communication sessions.
Developers can sometimes work around this device shortcoming in their (non-Windows) PC or phone application by having the PC or Mobile app delete any previous pairings with the device already retained, and negotiate a new pairing each time it sees the Bluetooth device. This is possible because many Bluetooth devices have a static PIN, require no interaction for pairing, and remain in open pairing mode. So the app creates a new device pairing upon each communication. The Mac BLE API requires no user interaction for pairing and un-pairing as well.
But this solution is unworkable under Windows BLE API, because unlike regular Bluetooth, the Bluetooth Low Energy API requires user interaction during both the pairing, and un-pairing "ceremonies". The user must agree to every pairing, and must agree to every un-pairing. This makes this workaround solution a non-starter from a UX standpoint on Windows. My guess is the BLE device manufacturer isn't storing the bonding.
We ran into such a situation ourselves developing our own BLE driver to speak with our own BLE board; we had to re-do the firmware running our BLE device because while it would work under Mac OS and Android with the method described above, the BLE API available on the Microsoft UWP requires user interaction during the pairing ceremony. This seems the right way to do things, anyway.
I'm not sure how to correctly phrase this question, as I'm just starting to learn Bluetooth and its ways, but... imagine holding in an iPhone or Android phone in your hand in a large building with many rooms. You pair your device with a Bluetooth master device via an antenna in that room. Then once you move from room to room, your device communicates with other antennas throughout the building, but the device treats it as one pairing.
Is this at all possible? Was Bluetooth developed with this in mind at all?
Would this still work if the antennas were wireless? My idea is for devices to communicate with nodes via Bluetooth, and nodes interact with central base via wi-fi/local router.
Also, third random question: how does using BLE affect any of this?
Please tell me if I'm crazy! Thanks!
Bluetooth 4.0 BLE allows for a slave to connect to one master. 4.1 BLE allows for more than one connection, but I don't know if anything implements that yet.
Either way, there's no sort of "roaming" method pairing devices like with wifi access points with the same SSID. BLE however doesn't require pairing like regular Bluetooth, so you could just connect to a new access point each time you lose a connection.
You can also communicate via advertising packets from the "antenna" in each room. This would facilitate information being passed from those rooms to the phone, but not the other way around. This is basically how you communicate with BLE when you don't pair/connect devices and is how iBeacons work.
If you're writing the software yourself, and installing it in the building and on the phone, then I think it should be totally possible. Bluetooth devices can detect the distance and direction of other bluetooth devices. So if both devices are running software that is designed to, and grants permission to do so, it should be no-big-deal to programmatically auto-reconnect to the new nearest antenna whenever one becomes significantly closer than the one that your phone is currently connected to. As for software that already does this that you wouldn't have to develop from scratch yourself, no idea.