Bluetooth LE can't send data from central to peripheral - ios

Question

I am dealing with BluetoothLow Energy problem. I find my peripheral BLE device with iPhone, connect to it, also find service and the characteristic which is in write mode. But when I try to send some data, nothing happens - device doesn't receive anything and also - (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error is not called.
My writeValue method is here:
-(void) writeValue:(int)serviceUUID characteristicUUID:(int)characteristicUUID p:(CBPeripheral *)p data:(NSData *)data {
CBUUID *UUIDService = [CBUUID UUIDWithString:[NSString stringWithFormat:#"%#",TRANSFER_SERVICE_UUID]];
CBUUID *UUIDCharacteristic = [CBUUID UUIDWithString:[NSString stringWithFormat:#"%#",TRANSFER_CHARACTERISTIC_UUID]];
NSLog(#"ALERT");
CBService *service = [self findServiceFromUUID:UUIDService p:p];
if (!service)
{
NSLog(#"Could not find service with UUID %# on peripheral with UUID %#",
[self CBUUIDToString:UUIDService],
p.identifier.UUIDString);
return;
}
CBCharacteristic *characteristic = [self findCharacteristicFromUUID:UUIDCharacteristic service:service];
if (!characteristic)
{
NSLog(#"Could not find characteristic with UUID %# on service with UUID %# on peripheral with UUID %#",
[self CBUUIDToString: UUIDCharacteristic],
[self CBUUIDToString:UUIDService],
p.identifier.UUIDString);
return;
}
NSString *message = #"AB";
NSData *dataMsg= [message dataUsingEncoding:NSUTF8StringEncoding];
[p writeValue:dataMsg forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];
}
What could be the problem?

Answer 1

Try to this. swift 3
This code for enable notify for CBCharacteristic(0x12 for notify property).
func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
for newChar: CBCharacteristic in service.characteristics!{
peripheral.readValue(for: newChar)
if newChar.properties.rawValue == 0x12{
peripheral.setNotifyValue(true, for: newChar)
}
}
}