How to get started on a GATT Server ?

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"

Any pointers to help me get started would be appreciated. Thanks!

Kind regards,
Edmund

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Edmund Urbani
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Hi Edmund,

Quoted 8 lines · Edmund

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.

Quoted 6 lines

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.

Quoted 4 lines

Any pointers to help me get started would be appreciated. Thanks!

Kind regards,
Edmund

Cheers,
Arman

Quoted 41 lines · Arman Uguray

Hi Edmund,

Quoted 10 lines

On Mon, Nov 3, 2014 at 7:38 AM, Urbani, Edmund
<[email protected]> 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.

Quoted 8 lines

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.

Quoted 4 lines

Any pointers to help me get started would be appreciated. Thanks!

Kind regards,
Edmund

Quoted 2 lines

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?

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?

Kind regards,
Edmund

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Hi Edmund,

Quoted 36 lines · Edmund

Quoted 35 lines · Arman Uguray

Hi Edmund,

Quoted 10 lines

On Mon, Nov 3, 2014 at 7:38 AM, Urbani, Edmund
<[email protected]> 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.

Quoted 8 lines

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.

Quoted 2 lines

Any pointers to help me get started would be appreciated. Thanks!

Quoted 9 lines

Quoted 4 lines

Quoted 2 lines

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.

Quoted 3 lines

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.

Quoted 4 lines

Kind regards,
Edmund

Quoted 5 lines

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Cheers,
Arman

Quoted 89 lines · Arman Uguray

Hi Edmund,

Quoted 45 lines · Edmund

Quoted 43 lines · Arman Uguray

Hi Edmund,

Quoted 11 lines

On Mon, Nov 3, 2014 at 7:38 AM, Urbani, Edmund
<[email protected]> 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.

Quoted 9 lines

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.

Quoted 4 lines

Any pointers to help me get started would be appreciated. Thanks!

Kind regards,
Edmund

Quoted 8 lines

Quoted 2 lines

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.

Quoted 3 lines

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.

Quoted 10 lines

Kind regards,
Edmund

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To unsubscribe from this list: send the line "unsubscribe linux-bluetooth"
in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html

Quoted 2 lines

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

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To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html

Hi Edmund,

Quoted 86 lines · Edmund

Quoted 75 lines · Arman Uguray

Hi Edmund,

Quoted 38 lines · Edmund

Quoted 37 lines · Arman Uguray

Hi Edmund,

Quoted 11 lines

On Mon, Nov 3, 2014 at 7:38 AM, Urbani, Edmund
<[email protected]> 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.

Quoted 9 lines

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.

Quoted 2 lines

Any pointers to help me get started would be appreciated. Thanks!

Quoted 9 lines

Quoted 4 lines

Quoted 2 lines

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.

Quoted 3 lines

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.

Quoted 4 lines

Kind regards,
Edmund

Quoted 8 lines

Quoted 6 lines

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in
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More majordomo info at http://vger.kernel.org/majordomo-info.html

Cheers,
Arman

Quoted 9 lines

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?

It's not obvious from reading the existing code but the "gatt_service_add" function defined attrib/gatt-service.h allows you to specify read/write handlers using options passed via its variable length argument list. You can look at profiles/proximity/linkloss.c for an example of this. Looking at the link_loss_register function, I see the profile register both a read and a write callback for the Alert Level characteristic (the functions link_loss_alert_lvl_read and link_loss_alert_lvl_write). I think this is what you're looking for.

That said, the new API will hopefully make this more readable by doing away with the variable argument list and having explicit functions and arguments for inserting characteristics into the database with read/write handlers.

Quoted 3 lines

Kind regards,
Edmund

Quoted 5 lines

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Cheers,
Arman

Quoted 137 lines · Arman Uguray

Hi Edmund,

Quoted 104 lines

On Wed, Nov 5, 2014 at 9:21 AM, Urbani, Edmund
<[email protected]> wrote:

Quoted 92 lines · Arman Uguray

Hi Edmund,

Quoted 47 lines · Edmund

Quoted 45 lines · Arman Uguray

Hi Edmund,

Quoted 12 lines

On Mon, Nov 3, 2014 at 7:38 AM, Urbani, Edmund
<[email protected]> 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.

Quoted 10 lines

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.

Quoted 4 lines

Any pointers to help me get started would be appreciated. Thanks!

Kind regards,
Edmund

Quoted 9 lines

Quoted 2 lines

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.

Quoted 3 lines

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.

Quoted 10 lines

Kind regards,
Edmund

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To unsubscribe from this list: send the line "unsubscribe linux-bluetooth"
in
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Quoted 2 lines

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 :/ ).

Quoted 6 lines

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?

It's not obvious from reading the existing code but the "gatt_service_add" function defined attrib/gatt-service.h allows you to specify read/write handlers using options passed via its variable length argument list. You can look at profiles/proximity/linkloss.c for an example of this. Looking at the link_loss_register function, I see the profile register both a read and a write callback for the Alert Level characteristic (the functions link_loss_alert_lvl_read and link_loss_alert_lvl_write). I think this is what you're looking for.

That said, the new API will hopefully make this more readable by doing away with the variable argument list and having explicit functions and arguments for inserting characteristics into the database with read/write handlers.

Quoted 9 lines

Kind regards,
Edmund

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Quoted 2 lines

Cheers,
Arman

Alright, I have a GATT service up and running with handlers for read and write requests, and an iOS app that acts as the client/central.

The only thing that is still now working the way it should is service discovery. Currently the client finds the service by connecting to any device which advertises itself as connectable and then queries its service UUIDs. Apparently my service UUID (currently still 16 bit) is not advertised, and so I have to resort to this kind of slow, battery-consuming service discovery. How do I get BlueZ to include the service UUID in LE advertisements?

This is the last obstacle to a demo-ready prototype for my project. Thanks for everything so far!

And as for future development and production use - any guesses when a BlueZ version with a stable GATT service interface over D-Bus might be released?

Kind regards,
Edmund Urbani

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