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lucasssvazlucasssvaz
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feat(ble): Add simultaneous client and server example (#12141)
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‎libraries/BLE/examples/Client_Server/Client_Server.ino‎

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/*
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* BLE Client and Server Coexistence Example
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*
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* This example demonstrates how to run both BLE client and server
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* functionality on the same ESP32 device simultaneously.
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*
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* The device will:
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* - Act as a BLE server, advertising a service with a characteristic
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* - Act as a BLE client, scanning for other BLE servers
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* - Connect to found servers and interact with their services
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* - Handle both incoming and outgoing connections
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*
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* You can test this example by uploading it to two ESP32 boards.
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*
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* Author: lucasssvaz
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* Based on Arduino BLE examples
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*/
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#include <BLEDevice.h>
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#include <BLEUtils.h>
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#include <BLEServer.h>
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#include <BLEClient.h>
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#include <BLEScan.h>
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// Server-side definitions
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#define SERVER_SERVICE_UUID "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
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#define SERVER_CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"
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// Client-side definitions (looking for the same service)
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static BLEUUID clientServiceUUID(SERVER_SERVICE_UUID);
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static BLEUUID clientCharUUID(SERVER_CHARACTERISTIC_UUID);
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// Server objects
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BLEServer *pServer = nullptr;
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BLECharacteristic *pServerCharacteristic = nullptr;
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// Client objects
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static boolean doConnect = false;
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static boolean clientConnected = false;
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static BLERemoteCharacteristic *pRemoteCharacteristic;
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static BLEAdvertisedDevice *targetDevice;
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static BLEClient *pClient = nullptr;
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BLEScan *pBLEScan = nullptr;
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// Server callbacks
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class ServerCallbacks : public BLEServerCallbacks {
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void onConnect(BLEServer *pServer) {
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Serial.println("Server: Client connected");
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}
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void onDisconnect(BLEServer *pServer) {
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Serial.println("Server: Client disconnected");
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// Restart advertising
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BLEDevice::startAdvertising();
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}
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};
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// Characteristic callbacks for server
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class CharacteristicCallbacks : public BLECharacteristicCallbacks {
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void onWrite(BLECharacteristic *pCharacteristic) {
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String value = pCharacteristic->getValue();
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Serial.print("Server: Characteristic written, value: ");
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Serial.println(value.c_str());
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}
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void onRead(BLECharacteristic *pCharacteristic) {
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Serial.println("Server: Characteristic read");
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}
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};
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// Client callbacks
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class ClientCallbacks : public BLEClientCallbacks {
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void onConnect(BLEClient *pClient) {
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Serial.println("Client: Connected to server");
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clientConnected = true;
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}
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void onDisconnect(BLEClient *pClient) {
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Serial.println("Client: Disconnected from server");
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clientConnected = false;
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}
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};
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// Client notification callback
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static void notifyCallback(BLERemoteCharacteristic *pBLERemoteCharacteristic, uint8_t *pData, size_t length, bool isNotify) {
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Serial.print("Client: Notify callback for characteristic ");
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Serial.print(pBLERemoteCharacteristic->getUUID().toString().c_str());
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Serial.print(" of data length ");
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Serial.println(length);
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Serial.print("Client: Data: ");
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Serial.write(pData, length);
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Serial.println();
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}
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// Scan callbacks
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class AdvertisedDeviceCallbacks : public BLEAdvertisedDeviceCallbacks {
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void onResult(BLEAdvertisedDevice advertisedDevice) {
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Serial.print("Client: Found device: ");
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Serial.println(advertisedDevice.toString().c_str());
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// Check if this device has our target service
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if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(clientServiceUUID) && !clientConnected) {
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Serial.println("Client: Found target service, attempting connection...");
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BLEDevice::getScan()->stop();
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targetDevice = new BLEAdvertisedDevice(advertisedDevice);
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doConnect = true;
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}
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}
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};
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bool connectToServer() {
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Serial.print("Client: Forming connection to ");
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Serial.println(targetDevice->getAddress().toString().c_str());
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// Create client if it doesn't exist, otherwise reuse existing one
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if (pClient == nullptr) {
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pClient = BLEDevice::createClient();
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pClient->setClientCallbacks(new ClientCallbacks());
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Serial.println("Client: Created new client");
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} else {
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Serial.println("Client: Reusing existing client");
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}
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if (!pClient->connect(targetDevice)) {
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Serial.println("Client: Failed to connect");
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return false;
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}
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Serial.println("Client: Connected to server");
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pClient->setMTU(517); // Request maximum MTU
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// Get the service
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BLERemoteService *pRemoteService = pClient->getService(clientServiceUUID);
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if (pRemoteService == nullptr) {
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Serial.print("Client: Failed to find service UUID: ");
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Serial.println(clientServiceUUID.toString().c_str());
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pClient->disconnect();
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return false;
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}
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Serial.println("Client: Found service");
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// Get the characteristic
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pRemoteCharacteristic = pRemoteService->getCharacteristic(clientCharUUID);
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if (pRemoteCharacteristic == nullptr) {
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Serial.print("Client: Failed to find characteristic UUID: ");
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Serial.println(clientCharUUID.toString().c_str());
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pClient->disconnect();
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return false;
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}
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Serial.println("Client: Found characteristic");
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// Read the initial value
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if (pRemoteCharacteristic->canRead()) {
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String value = pRemoteCharacteristic->readValue();
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Serial.print("Client: Initial characteristic value: ");
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Serial.println(value.c_str());
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}
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// Register for notifications if available
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if (pRemoteCharacteristic->canNotify()) {
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pRemoteCharacteristic->registerForNotify(notifyCallback);
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Serial.println("Client: Registered for notifications");
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}
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return true;
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}
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void setupServer() {
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Serial.println("Setting up BLE Server...");
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// Create server
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pServer = BLEDevice::createServer();
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pServer->setCallbacks(new ServerCallbacks());
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// Create service
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BLEService *pService = pServer->createService(SERVER_SERVICE_UUID);
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// Create characteristic
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pServerCharacteristic = pService->createCharacteristic(
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SERVER_CHARACTERISTIC_UUID, BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY
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);
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pServerCharacteristic->setCallbacks(new CharacteristicCallbacks());
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pServerCharacteristic->setValue("Hello from Coexistence Server");
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// Start service
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pService->start();
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// Start advertising
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BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
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pAdvertising->addServiceUUID(SERVER_SERVICE_UUID);
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pAdvertising->setScanResponse(true);
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pAdvertising->setMinPreferred(0x06);
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pAdvertising->setMinPreferred(0x12);
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BLEDevice::startAdvertising();
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Serial.println("Server: Advertising started");
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}
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void setupClient() {
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Serial.println("Setting up BLE Client...");
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// Create scanner
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pBLEScan = BLEDevice::getScan();
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pBLEScan->setAdvertisedDeviceCallbacks(new AdvertisedDeviceCallbacks());
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pBLEScan->setActiveScan(true);
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pBLEScan->setInterval(100);
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pBLEScan->setWindow(99);
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Serial.println("Client: Scanner configured");
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}
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void setup() {
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Serial.begin(115200);
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Serial.println("Starting BLE Client-Server Coexistence Example...");
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// Initialize BLE device with a name
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BLEDevice::init("ESP32-Coexistence");
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// Setup both server and client
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setupServer();
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setupClient();
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// Start initial scan
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pBLEScan->start(10, false); // Scan for 10 seconds, don't repeat
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Serial.println("Setup complete. Device is advertising as server and scanning as client.");
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}
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void loop() {
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static unsigned long lastServerUpdate = 0;
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static unsigned long lastClientWrite = 0;
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static unsigned long lastScanStart = 0;
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unsigned long currentTime = millis();
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// Handle client connection attempts
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if (doConnect && !clientConnected) {
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if (connectToServer()) {
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Serial.println("Client: Successfully connected to remote server");
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} else {
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Serial.println("Client: Failed to connect, will retry scanning");
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// Restart scanning after failed connection
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pBLEScan->start(10, false);
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}
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doConnect = false;
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}
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// Update server characteristic periodically
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if (currentTime - lastServerUpdate > 5000) { // Every 5 seconds
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String value = "Server time: " + String(millis() / 1000);
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pServerCharacteristic->setValue(value.c_str());
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pServerCharacteristic->notify(); // Notify connected clients
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Serial.print("Server: Updated characteristic to: ");
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Serial.println(value);
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lastServerUpdate = currentTime;
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}
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// Write to remote characteristic if connected as client
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if (clientConnected && pRemoteCharacteristic && currentTime - lastClientWrite > 3000) {
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if (pRemoteCharacteristic->canWrite()) {
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String clientValue = "Client msg: " + String(millis() / 1000);
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pRemoteCharacteristic->writeValue(clientValue.c_str(), clientValue.length());
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Serial.print("Client: Wrote to remote characteristic: ");
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Serial.println(clientValue);
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lastClientWrite = currentTime;
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}
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}
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// Restart scanning periodically if not connected
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if (!clientConnected && currentTime - lastScanStart > 15000) { // Every 15 seconds
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Serial.println("Client: Restarting scan...");
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pBLEScan->start(10, false);
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lastScanStart = currentTime;
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}
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delay(100);
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}

‎libraries/BLE/examples/Client_Server/ci.yml‎

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fqbn_append: PartitionScheme=huge_app
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requires_any:
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- CONFIG_SOC_BLE_SUPPORTED=y
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- CONFIG_ESP_HOSTED_ENABLE_BT_NIMBLE=y

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