Bluetooth Low Energy in C - Using Bluez to Create a Gatt Server

Bluetooth Low Energy in C - using Bluez to create a GATT server

I got the example GATT server running for BlueZ 5.31 (latest as of this post):

My environment:

Vagrant

Virtual Box

Ubuntu Trusty Tahr as a guest OS (v. 14.04 32-bit OS)

Updated to linux kernel 3.19

Installed packages:

* libglib2.0-dev

* libdbus-1-dev

* libudev-dev

* libical-dev

* libreadline-dev

Downloaded BlueZ 5.31 from here: https://www.kernel.org/pub/linux/bluetooth/bluez-5.31.tar.xz

Installation of updated kernel (v. 3.19):

sudo apt-get update

sudo apt-get install --install-recommends linux-generic-lts-vivid

A reboot is necessary. I'm using Vagrant and lost shared folder access. If this happens to you, wait for vagrant to report the error and go into the VM anyway (vagrant ssh). In the VM, issue this command to fix the shared folder problem:

sudo /etc/init.d/vboxadd setup

I would reboot again (probably not necessary), to check that the shared folder is active again.

Once back in the VM, continue the installation of BlueZ 5.31:

cd ~

sudo apt-get install libglib2.0-dev libdbus-1-dev libudev-dev libical-dev libreadline-dev

wget https://www.kernel.org/pub/linux/bluetooth/bluez-5.31.tar.xz

tar xvf bluez-5.31.tar.xz

cd bluez-5.31

./configure --prefix=/usr --mandir=/usr/share/man --sysconfdir=/etc --localstatedir=/var --disable-systemd --enable-experimental --enable-maintainer-mode

make

sudo make install

sudo cp attrib/gatttool /usr/bin

Installation completed. Check it as follows:

hciconfig

You should get the follow response (or something similar):

hci0: Type: BR/EDR Bus: USB

BD Address: 00:1A:7D:DA:71:0C ACL MTU: 310:10 SCO MTU: 64:8

DOWN

RX bytes:15528 acl:126 sco:0 events:683 errors:0

TX bytes:6459 acl:146 sco:0 commands:234 errors:0

Configure the Bluetooth adapter, start advertising, start example GATT server (heart rate service) with verbose on (my adapter is hci0):

cd BlueZ 5.31 directory

sudo tools/btmgmt -i hci0 power off

sudo tools/btmgmt -i hci0 le on

sudo tools/btmgmt -i hci0 connectable on

sudo tools/btmgmt -i hci0 name "some friendly name"

sudo tools/btmgmt -i hci0 advertising on

sudo tools/btmgmt -i hci0 power on

tools/btgatt-server -i hci0 -s low -t public -r -v

Go to another device (I've used an iPod, an Android -- Samsung Galaxy 5S and Nexus tablet -- and another PC running BlueZ) and connect to the service. Here is how I did it on another PC running BlueZ:

gatttool -b MAC address of GATT server -I

connect

primary

characteristics

You can issue other commands to read and write to the GATT server.

I've also created a custom GATT server (your original request) by copying and editing this file: tools/btgatt-server.c. You can edit the Makefile.tools file to include your custom server in the build. You'll have to run automake, make, and sudo make install to get it running.

Bluetooth Low Energy: Use BlueZ stack as a peripheral (with custom services and characteristics)

You can see gatt-example practice, or defined profiles under profile/ directory such as alert/server.c. Basically, you just have to register your service using gatt_service_add() function, following the existing code. For example :

 gatt_service_add(adapter, GATT_PRIM_SVC_UUID, 0xFFFF,
    /* Char 1 */
    GATT_OPT_CHR_UUID16, 0xAAAA,
    GATT_OPT_CHR_PROPS, ATT_CHAR_PROPER_READ,
    GATT_OPT_CHR_VALUE_CB, ATTRIB_READ, read_func_callback,

    /* Char 2 Define here */
    ...
    /* Char 3 Define here */
    ...
    GATT_OPT_INVALID);
 }

Also, I forgot the details but in order to get alert server working, you need to enable experimental (and maintainer mode?) during configuration by adding "--enable-maintainer-mode" and "--enable-experimental"

To run, run the compiled "bluetoothd" with -n and -d options to debug (also -E for enabling experimental services). You may want to reset your adapter again after running bluetoothd. And then you can connect from remote device using gatttool (also with bluetoothd running on remote device).

BlueZ: How to set up a GATT server from the command line

So this is now handled with the new bluetoothctl tool. A gatt table can be set up using this tool as follows:-

#bluetoothctl
[bluetoothctl] menu gatt
[bluetoothctl] register-service 0xFFFF # (Choose yes when asked if primary service)
[bluetoothctl] register-characteristic 0xAAAA read       # (Select a value of 1 when prompted)
[bluetoothctl] register-characteristic 0xBBBB read,write # (Select a value of 0 when prompted)
[bluetoothctl] register-characteristic 0xCCCC read       # (Select a value of 2 when prompted)
[bluetoothctl] register-application # (This commits the services/characteristics and registers the profile)
[bluetoothctl] back
[bluetoothctl] advertise on

I've tried this with a few service/characteristic combinations and was able to get it to work. The GAP (0x1800) and GATT (0x1801) services are available by default and will be part of the GATT table when you advertise. You can also use the following command to see the available services:-

[bluetoothctl] show
Controller 00:AA:BB:CC:DD:EE (public)
    Name: MyMachine
    Alias: MyMachine
    Class: 0x000c0000
    Powered: yes
    Discoverable: no
    Pairable: yes
    UUID: Headset AG                (00001112-0000-1000-8000-00805f9b34fb)
    UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
    UUID: A/V Remote Control        (0000110e-0000-1000-8000-00805f9b34fb)
    UUID: Generic Access Profile    (00001800-0000-1000-8000-00805f9b34fb)
    UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
    UUID: A/V Remote Control Target (0000110c-0000-1000-8000-00805f9b34fb)
    UUID: Audio Source              (0000110a-0000-1000-8000-00805f9b34fb)
    UUID: Audio Sink                (0000110b-0000-1000-8000-00805f9b34fb)
    **UUID: Unknown                   (0000ffff-0000-1000-8000-00805f9b34fb)**
    UUID: Headset                   (00001108-0000-1000-8000-00805f9b34fb)
    Modalias: usb:v1D6Bp0246d0532
    Discovering: no

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