Bluez: advertise service / gatt server example?

Question

Goal

I am developping a simple device running Linux. It is BLE capable, and I am currently using bluez 5.8.

I want to trigger an action on this device using an iPhone.

What already works:

I can make the iPhone "see" the device.
The iPhone also connects to the device.

I setup the bluetooth device like this on linux (thanks to this question):

# activate bluetooth
hciconfig hci0 up                                             
# set advertise data: "hello world"
hcitool -i hci0 cmd 0x08 0x0008 48 45 4c 4c 4f 57 4f 52 4c 44
# start advertising as connectable
hciconfig hci0 leadv 0

The iOS code is straightforward:

- (int) scanForPeripherals
{
    if (self->centralManager.state != CBCentralManagerStatePoweredOn) {
        return -1;
    }
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:NO], CBCentralManagerScanOptionAllowDuplicatesKey, nil];
    [self.centralManager scanForPeripheralsWithServices:nil options:options];
    return 0;
}

- (void)centralManagerDidUpdateState:(CBCentralManager *)central
{
    if (central.state == CBCentralManagerStatePoweredOn) {
        NSLog(@"Starting scan");
        [self scanForPeripherals];
    }
}

- (void) centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI
{
    NSLog(@"didDiscoverPeripheral");
    /* 
     * Retain the peripheral to avoid the error:
     *  CoreBluetooth[WARNING]: state = connecting> is being dealloc'ed while connecting
     */
    self.activePeripheral = peripheral;
    [centralManager connectPeripheral:peripheral options:nil];
}

- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{
    NSLog(@"Connected to peripheral");

    /* discover all services */
    [peripheral discoverServices:nil];
}

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
{
    NSLog(@"Discovered services");
    for (CBService *service in peripheral.services) {
        NSLog(@"Discovered service %@", service);
    }
}

When running this code on the iPhone, I get this log:

2013-12-19 12:53:22.609 Test2[18518:60b] Starting scan
2013-12-19 12:53:29.945 Test2[18518:60b] didDiscoverPeripheral
2013-12-19 12:53:31.230 Test2[18518:60b] Connected to peripheral

So it seems that the iPhone connects fine, but does not see any service.

What I am missing

I need to advertise a simple BLE service, but I can't find any documentation on how to do this in bluez .
I think I need something like a gatt-server to receive read/write characteristics for the service I would advertise. I saw the plugins/gatt-example.c file in bluez, but I have absolutely no idea how to use it: there is no documentation.

I should probably mention that I saw this question: Creating a gatt server, but the answers raise too much questions (for example, where is the GATT api for bluez? how to set the GATT database? How to register for read/write events?)

EDIT: The commands I use only set-up the BLE device to advertise some data, but iOS reports that the connection is accepted. What part of bluez is accepting incoming connections?

Bluez: advertise service / gatt server example?

2 Answers