Central.m

- (void)sendMessage:(NSString *)context {
    if ([self.peripherals count] < 1 || context == nil) {
        return;
    }

    NSData *xmlData = [context dataUsingEncoding:NSUTF8StringEncoding];
    CBPeripheral *peripheral = [self.peripherals firstObject];
    [peripheral writeValue:xmlData forCharacteristic:self.cbCharacteristic type:CBCharacteristicWriteWithResponse];
}