Re: How to get started on a GATT Server ?

["Urbani, Edmund" <edmund.urbani@lilandit.com>]

On 11/04/2014 08:11 PM, Arman Uguray wrote:
> Hi Edmund,
>
> On Tue, Nov 4, 2014 at 4:04 AM, Urbani, Edmund
> <edmund.urbani@lilandit.com> wrote:
>> On 11/03/2014 08:32 PM, Arman Uguray wrote:
>>> Hi Edmund,
>>>
>>>> On Mon, Nov 3, 2014 at 7:38 AM, Urbani, Edmund
>>>> <edmund.urbani@lilandit.com> wrote:
>>>> Hello all,
>>>>
>>>> I am trying to write a simple GATT-based service of my own. Right now I
>>>> don't really know which docs I should be looking at. I have skimmed
>>>> through
>>>> bluez sources (5.23) and found gatt-service.h and gatt.h, as well as the
>>>> gatt-example plugin.
>>>>
>>>> So far I am still trying to figure out whether I should be going the C
>>>> API
>>>> route or maybe use the D-Bus interface. Also gatt-service.c seems to
>>>> suggest
>>>> that there is a way to register a GATT service over D-Bus but running it
>>>> gives me this:
>>>> RegisterService: Method "RegisterService" with signature "oa{sv}" on
>>>> interface "org.bluez.GattManager1" doesn't exist"
>>> The reason you're not seeing GattManager1 is because it's hidden
>>> behind the "experimental" flag. So you need to configure and run bluez
>>> with the --enable-experimental and the --experimental flags
>>> respectively.
>>>
>>> That said, that API implementation isn't complete and isn't in fact
>>> even wired up with the internal attrib-server. We're working towards
>>> rewriting all of the C API and finally implementing the proposed D-Bus
>>> API but until then, I would ignore doc/gatt-api.txt (it's only a
>>> proposal at the moment and isn't even included in release tarballs).
>>> So for now you have to use the C API route. There will probably be an
>>> announcement once that D-Bus API is finally supported.
>>
>>>> Any pointers to help me get started would be appreciated. Thanks!
>>>>
>>>> Kind regards,
>>>>     Edmund
>>> Cheers,
>>> Arman
>>
>> Thanks, I won't bother with the D-Bus interface then. But if the C API is
>> being rewritten now, that sounds like there is currently no stable API
>> available at all. :/ Or is it just the internals being rewritten?
>>
> The C API for GATT interactions is being rewritten, i.e. the code in
> attrib/* is being deprecated in favor of code in src/shared/gatt*. You
> can still keep using the existing APIs though at some point we will
> rip out the existing attrib-server to be a combination of
> shared/gatt-db and shared/gatt-server. So, make sure you keep track of
> the patches going in.
>
> Keep in mind that if you're developing your code on top of the master
> branch then things are meant to be in flight and unstable there, so
> you should follow releases anyway. I think we'll figure out a way so
> that the C based GATT server/client won't be entirely broken for
> people in between official BlueZ releases.
>
>> So I assume, the fastest route the get a prototype that does something,
>> would be to get gatt-example.c to run and then modify that, right?
>>
> Yes, that is the easiest way right now. When the new C APIs are mature
> enough we will convert gatt-example to use the new code but that's
> still a few months down the line.
>
>> Kind regards,
>>   Edmund
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-bluetooth"
>> in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Cheers,
> Arman

Thanks, Arman. I now have a basic service with one characteristic and a 
read-only value up and running (I can see and read its value from another system 
using gatttool... though my iOS app still fails to discover the service :/ ).

What I actually need however is a read/write attribute and a way to react to 
write requests. The examples in gatt-service.c all seem to be read-only. How 
would I get a call-back for an incoming write request?

Kind regards,
  Edmund