Re: Background CoreBluetooth
Re: Background CoreBluetooth
- Subject: Re: Background CoreBluetooth
- From: Darren Jones via Bluetooth-dev <email@hidden>
- Date: Fri, 8 May 2020 00:25:06 +0100
Thanks for the write up. Your findings are pretty much the same as mine.
I wonder how long the ‘keep alive’ can last. Possibly forever?
If you are in a household with multiple iOS users that install the app, an
initial connection could stay connected constantly while in range. I wonder
what effect that would have on battery life.
They’ve been very clever with the way Android can wake up iOS, so in a crowded
area with many devices there’s a good chance the app will work.
Walking to a local shop on your own and bumping into a few people, there’s a
good chance it won’t.
Sent from my iPhone
> On 8 May 2020, at 00:09, Nick Brook <email@hidden> wrote:
>
> I’ve been playing around with this today, testing with my own code and
> looking at the NHS App.
>
> The NHS App is doing nothing special, as far as I can see
> It advertises a service, and in the background iOS puts the service in the
> “overflow” (one-hot encoded)
> Android looks for this specific one hot encoded value. Actually, it doesn’t
> look for a specific bit set, but a fixed set of bytes, so if other Apps are
> advertising services in the background on iOS the NHS App on Android might
> fail to discover it. This seems like a bug, although I’m not sure if they
> could work around it
> It attempts to keep connections (and the process) alive for as long as
> possible by sending “keep alive” data every 8s (under the 10s execution
> window apple provides)
> It is susceptible to the problems other Apps are (restarting the phone,
> quitting the app etc can break scanning and discovery) but it helps to
> overcome this through notifications to the user to reopen the app.
> I’m not sure if Apple imposes a time limit on scanning for/advertising
> services in the background although presumably there is a notification for
> this in the NHS App if it does.
>
>
> With the user notifications, if users actually respond to them it might work
> well enough to be effective. But I could see users ignoring the notifications
> if there are too many, and particular when out and about and busy these may
> get ignored. If they are ignored, the App may not work for a long period of
> time.
>
> It seems the UK government may be reconsidering the centralised approach now
> anyway:
> https://www.telegraph.co.uk/news/2020/05/06/nhs-explores-feasibility-moving-contact-tracing-app-apple-google/?fbclid=IwAR2qT77qzPkMlefQWYRFKmy-zj3Y_z2-Ip2peuUE9nCdokHldxuEIC1Ze64
>
> I’d be keen to hear any further insight into how the App is working or
> background bluetooth can made to work better.
>
> Nick Brook
>
> NRB Tech
> W: https://nrbtech.io
>
>
>> On 7 May 2020, at 21:17, Darren Jones via Bluetooth-dev
>> <email@hidden> wrote:
>>
>> There is no location permission in the app.
>> Which is a good job as the questions over privacy would explode more than
>> they already have.
>>
>> Sent from my iPhone
>>
>>>> On 7 May 2020, at 21:14, Diego Alfarache <email@hidden> wrote:
>>>>
>>>
>>> These apps are going to have background location permission, which
>>> effectively gives them free reign to run almost anything in the background.
>>>
>>>
>>> I created a framework for a client that would act as both a peripheral and
>>> central while executing in the background, but only when they had “always”
>>> location permission.
>>>
>>> Diego
>>>
>>>
>>>
>>> From: "Jan Lübeck via Bluetooth-dev (Fyrastudio)"
>>> <email@hidden>
>>> Reply-To: "Jan Lübeck (Fyrastudio)" <email@hidden>
>>> Date: Thursday, May 7, 2020 at 3:04 PM
>>> To: Darren Jones <email@hidden>
>>> Cc: <email@hidden>
>>> Subject: Re: Background CoreBluetooth
>>>
>>> Apple did announce that they are sharing their APIs with specific
>>> developers. Maybe UK NHS is one of them?
>>> ______
>>> Jan Lübeck
>>> Chief Technology Officer
>>> fyrastudio.com
>>>
>>>
>>> On Thu, May 7, 2020 at 3:48 PM Darren Jones via Bluetooth-dev
>>> <email@hidden> wrote:
>>> Unless you have your head buried in the sand, I’m sure everyone has noticed
>>> the sagas going on with countries creating their own COVID-19 contact
>>> tracing apps.
>>>
>>> I have personally tried many times over the years to create an app that can
>>> broadcast and scan in the background to trigger a ‘contact trace’ and
>>> always failed. Yet the UK NHS are claiming they have an app that does just
>>> that.
>>>
>>> I’d love to hear from anyone that’s had experience with background BT. Is
>>> it possible? Can a background CBPeripheral be detected by a background
>>> CBCentral?
>>>
>>> If not, is there a definitive time period when discovery becomes impossible?
>>>
>>> Thanks
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