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Stop connection between BLE Client and Server of custom UUID. And connect client to different server.

KKaushik

I'm working on BLE based on ESP32.

I configured a custom Service and Characteristics with UUID.

Using 2 ESP32 Dev modules. I can connect them together, but the Client module doesn't disconnect and connect to the new UUID.

I need help disconnecting the Client from Server (UUID suppose 001) and connecting it to Server with UUID (let 002).

I couldn't find any function to disconnect clients from servers.

Below code for Client Node 

/**
 * A BLE client example that is rich in capabilities.
 * There is a lot new capabilities implemented.
 * author unknown
 * updated by chegewara
 */

#include "BLEDevice.h"
//#include "BLEScan.h"

// The remote service we wish to connect to.
static BLEUUID serviceUUID("4fafc201-1fb5-459e-8fcc-c5c9c331915b");
// The characteristic of the remote service we are interested in.
static BLEUUID    charUUID("beb5483e-36e1-4688-b7f5-ea07361b215b");

static boolean doConnect = false;
static boolean connected = false;
static boolean doScan = false;
static BLERemoteCharacteristic* pRemoteCharacteristic;
static BLEAdvertisedDevice* myDevice;

static void notifyCallback(
  BLERemoteCharacteristic* pBLERemoteCharacteristic,
  uint8_t* pData,
  size_t length,
  bool isNotify) {
    Serial.print("Notify callback for characteristic ");
    Serial.print(pBLERemoteCharacteristic->getUUID().toString().c_str());
    Serial.print(" of data length ");
    Serial.println(length);
    Serial.print("data: ");
    Serial.println((char*)pData);
}

class MyClientCallback : public BLEClientCallbacks {
  void onConnect(BLEClient* pclient) {

    Serial.println("Conecction with server");
  }

  void onDisconnect(BLEClient* pclient) {
    connected = false;
    Serial.println("onDisconnect");
  }
};

uint8_t count =0;

bool connectToServer() {
    
    Serial.print("Forming a connection to ");
    Serial.println(myDevice->getAddress().toString().c_str());
    
    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");
    pClient->setMTU(517); //set client to request maximum MTU from server (default is 23 otherwise)

    //
    if(count>5)
    {
      pClient->disconnect();
      static BLEUUID serviceUUID("4fafc201-1fb5-459e-8fcc-c5c9c331914b");
      static BLEUUID    charUUID("beb5483e-36e1-4688-b7f5-ea07361b214b");

      Serial.println("DISCONNECTION \n\n");
      return false;
    }
    
    // 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: ");
      Serial.println(serviceUUID.toString().c_str());
      pClient->disconnect();
      return false;
    }
    Serial.println(" - Found our service");


    // Obtain a reference to the characteristic in the service of the remote BLE server.
    pRemoteCharacteristic = pRemoteService->getCharacteristic(charUUID);
    if (pRemoteCharacteristic == nullptr) {
      Serial.print("Failed to find our characteristic UUID: ");
      Serial.println(charUUID.toString().c_str());
      pClient->disconnect();
      return false;
    }
    Serial.println(" - Found our characteristic");

    // Read the value of the characteristic.
    if(pRemoteCharacteristic->canRead()) {
      std::string value = pRemoteCharacteristic->readValue();
      Serial.print("The characteristic value was: ");
      Serial.println(value.c_str());
    }
    
    if(pRemoteCharacteristic->canNotify())
      pRemoteCharacteristic->registerForNotify(notifyCallback);
      
    
    
    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: ");
    Serial.println(advertisedDevice.toString().c_str());

    // We have found a device, let us now see if it contains the service we are looking for.
    if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(serviceUUID)) {

      BLEDevice::getScan()->stop();
      myDevice = new BLEAdvertisedDevice(advertisedDevice);
      doConnect = true;
      doScan = true;

    } // Found our server
  } // onResult
}; // MyAdvertisedDeviceCallbacks


void setup() {
  Serial.begin(115200);
  Serial.println("Starting Arduino BLE Client application...");
  BLEDevice::init("");

  // 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->setInterval(1349);
  pBLEScan->setWindow(449);
  pBLEScan->setActiveScan(true);
  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) {
    String newValue = "Time since boot: " + String(millis()/1000);
    Serial.println("Setting new characteristic value to \"" + newValue + "\"");
    
    // Set the characteristic's value to be the array of bytes that is actually a string.
    pRemoteCharacteristic->writeValue(newValue.c_str(), newValue.length());
  }else if(doScan){
    BLEDevice::getScan()->start(0);  // this is just example to start scan after disconnect, most likely there is better way to do it in arduino
  }
  count++;
  delay(1000); // Delay a second between loops.
} // End of loop

After Count reaches to greater than 5, I run below part for 

client->disconnect

 

if(count>5)
    {
      pClient->disconnect();
      static BLEUUID serviceUUID("4fafc201-1fb5-459e-8fcc-c5c9c331914b");
      static BLEUUID    charUUID("beb5483e-36e1-4688-b7f5-ea07361b214b");

      Serial.println("DISCONNECTION \n\n");
      return false;
    }

Below code for Server Node

/*
    Video: https://www.youtube.com/watch?v=oCMOYS71NIU
    Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleNotify.cpp
    Ported to Arduino ESP32 by Evandro Copercini
    updated by chegewara

   Create a BLE server that, once we receive a connection, will send periodic notifications.
   The service advertises itself as: 4fafc201-1fb5-459e-8fcc-c5c9c331914b
   And has a characteristic of: beb5483e-36e1-4688-b7f5-ea07361b26a8

   The design of creating the BLE server is:
   1. Create a BLE Server
   2. Create a BLE Service
   3. Create a BLE Characteristic on the Service
   4. Create a BLE Descriptor on the characteristic
   5. Start the service.
   6. Start advertising.

   A connect hander associated with the server starts a background task that performs notification
   every couple of seconds.
*/
#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

BLEServer* pServer = NULL;
BLECharacteristic* pCharacteristic = NULL;
bool deviceConnected = false;
bool oldDeviceConnected = false;
uint32_t value = 0;

// See the following for generating UUIDs:
// https://www.uuidgenerator.net/

#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b214b"


class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      Serial.println("Conecction with client");
      deviceConnected = true;
      BLEDevice::startAdvertising();
    };

    void onDisconnect(BLEServer* pServer) {
      Serial.println("Disconnection with client");
      deviceConnected = false;
    }
};


uint8_t once1 = 0;

void setup() {
  Serial.begin(115200);

  // Create the BLE Device
  BLEDevice::init("ESP32");

  // Create the BLE Server
  pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());

  // Create the BLE Service
  BLEService *pService = pServer->createService(SERVICE_UUID);

  // Create a BLE Characteristic
  pCharacteristic = pService->createCharacteristic(
                      CHARACTERISTIC_UUID,
                      BLECharacteristic::PROPERTY_READ   |
                      BLECharacteristic::PROPERTY_WRITE  |
                      BLECharacteristic::PROPERTY_NOTIFY |
                      BLECharacteristic::PROPERTY_INDICATE
                    );

  // https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.descriptor.gatt.client_characteristic_configuration.xml
  // Create a BLE Descriptor
  pCharacteristic->addDescriptor(new BLE2902());

  // Start the service
  pService->start();

  // Start advertising
  BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();

  pAdvertising->addServiceUUID(SERVICE_UUID);

  pAdvertising->setScanResponse(false);
  pAdvertising->setMinPreferred(0x0);  // set value to 0x00 to not advertise this parameter
  BLEDevice::startAdvertising();
  Serial.println("Waiting a client connection to notify...");
}

void loop() {
  // notify changed value
  //  if (deviceConnected) {
  //    pCharacteristic->setValue((uint8_t*)&value, 4);
  //    pCharacteristic->notify();
  //  }
  value++;
  delay(2000); // bluetooth stack will go into congestion, if too many packets are sent, in 6 hours test i was able to go as low as 3ms


  // disconnecting
  if (!deviceConnected && oldDeviceConnected) {
    delay(500); // give the bluetooth stack the chance to get things ready
    pServer->startAdvertising(); // restart advertising
    Serial.println("start advertising");
    oldDeviceConnected = deviceConnected;
  }
  // connecting
  if (deviceConnected && !oldDeviceConnected) {
    // do stuff here on connecting
    oldDeviceConnected = deviceConnected;
  }

}

Anyone can guide me how can I achieve this? All I need is resetting way for Service and Characteristics for either client or server node.

Parents
  • 0

    Hi,

    Regarding:

    After Count reaches to greater than 5, I run below part for client->disconnect

    Are you saying that the Arduino disconnect method isn't functioning for you? If so, it could be a bug in the Arduino libraries, you should raise it as an issue on the Arduino site or forum.

    I can think of (ugly) workarounds, but getting the library problem raised and fixed should be one of the first things to consider.

    For a workaround, perhaps you could store the state in some non-volatile storage (hopefully there is an Arduino library for that, I have not checked), and then force a reboot of your client, from code.

    Or, if it is possible, re-architect what you're doing, so you don't need to do it (you've not mentioned what your actual requirement is, just that you wish to connect to many servers one at a time).

Reply
  • 0

    Hi,

    Regarding:

    After Count reaches to greater than 5, I run below part for client->disconnect

    Are you saying that the Arduino disconnect method isn't functioning for you? If so, it could be a bug in the Arduino libraries, you should raise it as an issue on the Arduino site or forum.

    I can think of (ugly) workarounds, but getting the library problem raised and fixed should be one of the first things to consider.

    For a workaround, perhaps you could store the state in some non-volatile storage (hopefully there is an Arduino library for that, I have not checked), and then force a reboot of your client, from code.

    Or, if it is possible, re-architect what you're doing, so you don't need to do it (you've not mentioned what your actual requirement is, just that you wish to connect to many servers one at a time).

Children
  • 0 in reply to shabaz

    It's home automation with 5 to 6 numbers of server module (Sensor, displays, servos) with fixed UUIDs, and a Client node in central which connects and disconnect to each of them as per requirement. 

    shabaz said:
    Are you saying that the Arduino disconnect method isn't functioning for you? If so, it could be a bug in the Arduino libraries, you should raise it as an issue on the Arduino site or forum.

    What i understood is Client/server is supposed to revoke "DisconnectCallback' on disconnection. But it doesn't.

    Also When I tried to restart Service with new UUIDs at client node it doesn't connect to new UUID server either.

    That's why I figured its probably doesn't disconnect in the first place,