#include <ArduinoBLE.h>
BLEService stringService("19B10000-0001-537E-4F6C-D104768A1214"); // BLE String Service
BLEStringCharacteristic stringCharacteristic("19B10001-0001-537E-4F6C-D104768A1214", BLERead | BLEWrite, 512);
void setup() {
 Serial.begin(9600);
 while (!Serial);
 // begin initialization
 if (!BLE.begin()) {
 Serial.println("starting BLE failed!");
 while (1);
 }
 // set advertised local name and service UUID:
 BLE.setLocalName("String");
 BLE.setAdvertisedService(stringService);
 // add the characteristic to the service
 stringService.addCharacteristic(stringCharacteristic);
 // add service
 BLE.addService(stringService);
 // set the initial value for the characeristic:
 stringCharacteristic.writeValue("hello");
 // start advertising
 BLE.advertise();
 Serial.println("BLE String Peripheral");
}
void loop() {
 // listen for BLE peripherals to connect:
 BLEDevice central = BLE.central();
 // if a central is connected to peripheral:
 if (central) {
 Serial.print("Connected to central: ");
 // print the central's MAC address:
 Serial.println(central.address());
 // while the central is still connected to peripheral:
 while (central.connected()) {
 if (stringCharacteristic.written()) {
 Serial.println("stringCharacteristic written, new value = ");
 String value = stringCharacteristic.value();
 Serial.println(value);
 }
 }
 // when the central disconnects, print it out:
 Serial.print(F("Disconnected from central: "));
 Serial.println(central.address());
 }
}