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A BLE client example that is rich in capabilities.
There is a lot new capabilities implemented.
author unknown
updated by chegewara
#include "BLEDevice.h"
// The remote service we wish to connect to.
static BLEUUID serviceUUID("1812");
static boolean doConnect = false;
static boolean connected = false;
static boolean doScan = false;
static BLEAdvertisedDevice* myDevice;
static void notifyCallback(
BLERemoteCharacteristic* pBLERemoteCharacteristic,
uint8_t* pData,
size_t length,
bool isNotify) {
Serial.print("Notify callback for characteristic ");
Serial.print(") of data length ");
Serial.print(" data: ");
for ( int i = 0 ; i < length ; i++ ) {
Serial.printf( "%02X ", pData[i] );
class MyClientCallback : public BLEClientCallbacks {
void onConnect(BLEClient* pclient) {
void onDisconnect(BLEClient* pclient) {
connected = false;
bool connectToServer() {
Serial.print("Forming a connection to ");
BLEClient* pClient = BLEDevice::createClient();
Serial.println(" - Created client");
pClient->setClientCallbacks(new MyClientCallback());
// Connect to the remove BLE Server.
pClient->connect(myDevice); // if you pass BLEAdvertisedDevice instead of address, it will be recognized type of peer device address (public or private)
Serial.println(" - Connected to server");
// Obtain a reference to the service we are after in the remote BLE server.
BLERemoteService* pRemoteService = pClient->getService(serviceUUID);
if (pRemoteService == nullptr) {
Serial.print("Failed to find our service UUID: ");
return false;
Serial.println(" - Found our service");
std::map<uint16_t, BLERemoteCharacteristic*>* mapCharacteristics = pRemoteService->getCharacteristicsByHandle();
for (std::map<uint16_t, BLERemoteCharacteristic*>::iterator i = mapCharacteristics->begin(); i != mapCharacteristics->end(); ++i) {
if (i->second->canNotify()) {
Serial.println(" - Add Notify");
connected = true;
return true;
Scan for BLE servers and find the first one that advertises the service we are looking for.
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
Called for each advertising BLE server.
void onResult(BLEAdvertisedDevice advertisedDevice) {
Serial.print("BLE Advertised Device found: ");
// We have found a device, let us now see if it contains the service we are looking for.
if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(serviceUUID)) {
myDevice = new BLEAdvertisedDevice(advertisedDevice);
doConnect = true;
doScan = true;
} // Found our server
} // onResult
}; // MyAdvertisedDeviceCallbacks
void setup() {
Serial.println("Starting Arduino BLE Client application...");
// Retrieve a Scanner and set the callback we want to use to be informed when we
// have detected a new device. Specify that we want active scanning and start the
// scan to run for 5 seconds.
BLEScan* pBLEScan = BLEDevice::getScan();
pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
pBLEScan->start(5, false);
} // End of setup.
// This is the Arduino main loop function.
void loop() {
// If the flag "doConnect" is true then we have scanned for and found the desired
// BLE Server with which we wish to connect. Now we connect to it. Once we are
// connected we set the connected flag to be true.
if (doConnect == true) {
if (connectToServer()) {
Serial.println("We are now connected to the BLE Server.");
} else {
Serial.println("We have failed to connect to the server; there is nothin more we will do.");
doConnect = false;
// If we are connected to a peer BLE Server, update the characteristic each time we are reached
// with the current time since boot.
if (connected) {
} else if (doScan) {
BLEDevice::getScan()->start(0); // this is just eample to start scan after disconnect, most likely there is better way to do it in arduino
delay(1000); // Delay a second between loops.
} // End of loop
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