esp-nimble-cpp/examples/Advanced/NimBLE_Server/main/main.cpp

/** NimBLE_Server Demo:
 *
 *  Demonstrates many of the available features of the NimBLE server library.
 *  
 *  Created: on March 22 2020
 *      Author: H2zero
 * 
*/
#include "NimBLEDevice.h"
#include "NimBLELog.h"

#include <stdio.h>

extern "C" {void app_main(void);}

static NimBLEServer* pServer;

/**  None of these are required as they will be handled by the library with defaults. **
 **                       Remove as you see fit for your needs                        */  
class ServerCallbacks: public NimBLEServerCallbacks {
    void onConnect(NimBLEServer* pServer) {
        printf("Client connected\n");
        NimBLEDevice::startAdvertising();
    };
    /** Alternative onConnect() method to extract details of the connection. 
     *  See: src/ble_gap.h for the details of the ble_gap_conn_desc struct.
     */  
    void onConnect(NimBLEServer* pServer, ble_gap_conn_desc* desc) {
        printf("Client address: %s\n", NimBLEAddress(desc->peer_ota_addr).toString().c_str());
        /** We can use the connection handle here to ask for different connection parameters.
         *  Args: connection handle, min connection interval, max connection interval
         *  latency, supervision timeout.
         *  Units; Min/Max Intervals: 1.25 millisecond increments.
         *  Latency: number of intervals allowed to skip.
         *  Timeout: 10 millisecond increments, try for 3x interval time for best results.  
         */
        pServer->updateConnParams(desc->conn_handle, 24, 48, 0, 18);
    };
    void onDisconnect(NimBLEServer* pServer) {
        printf("Client disconnected - start advertising\n");
        NimBLEDevice::startAdvertising();
    };
    void onMTUChange(uint16_t MTU, ble_gap_conn_desc* desc) {
        printf("MTU updated: %u for connection ID: %u\n", MTU, desc->conn_handle);
    };
    
/********************* Security handled here **********************
****** Note: these are the same return values as defaults ********/
    uint32_t onPassKeyRequest(){
        printf("Server Passkey Request\n");
        /** This should return a random 6 digit number for security 
         *  or make your own static passkey as done here.
         */
        return 123456; 
    };

    bool onConfirmPIN(uint32_t pass_key){
        printf("The passkey YES/NO number: %d\n", pass_key);
        /** Return false if passkeys don't match. */
        return true; 
    };

    void onAuthenticationComplete(ble_gap_conn_desc* desc){
        /** Check that encryption was successful, if not we disconnect the client */  
        if(!desc->sec_state.encrypted) {
            /** NOTE: createServer returns the current server reference unless one is not already created */
            NimBLEDevice::createServer()->disconnect(desc->conn_handle);
            printf("Encrypt connection failed - disconnecting client\n");
            return;
        }
        printf("Starting BLE work!");
    };
};

/** Handler class for characteristic actions */
class CharacteristicCallbacks: public NimBLECharacteristicCallbacks {
    void onRead(NimBLECharacteristic* pCharacteristic){
        printf("%s : onRead(), value: %s\n", 
                            pCharacteristic->getUUID().toString().c_str(),
                            pCharacteristic->getValue().c_str());
    };

    void onWrite(NimBLECharacteristic* pCharacteristic) {
        printf("%s : onWrite(), value: %s\n", 
                            pCharacteristic->getUUID().toString().c_str(),
                            pCharacteristic->getValue().c_str());
    };
    /** Called before notification or indication is sent, 
     *  the value can be changed here before sending if desired.
     */
    void onNotify(NimBLECharacteristic* pCharacteristic) {
        printf("Sending notification to clients\n");
    };


    /** The status returned in status is defined in NimBLECharacteristic.h.
     *  The value returned in code is the NimBLE host return code.
     */
    void onStatus(NimBLECharacteristic* pCharacteristic, Status status, int code) {
        printf("Notification/Indication status code: %d , return code: %d, %s\n",
                            status,
                            code,
                            NimBLEUtils::returnCodeToString(code));
    };
};
    
/** Handler class for descriptor actions */    
class DescriptorCallbacks : public NimBLEDescriptorCallbacks {
    void onWrite(NimBLEDescriptor* pDescriptor) {
        std::string dscVal((char*)pDescriptor->getValue(), pDescriptor->getLength());
        printf("Descriptor witten value: %s\n", dscVal.c_str());
    };

    void onRead(NimBLEDescriptor* pDescriptor) {
        printf("%s Descriptor read\n", pDescriptor->getUUID().toString().c_str());
    };;
};


/** Define callback instances globally to use for multiple Charateristics \ Descriptors */ 
static DescriptorCallbacks dscCallbacks;
static CharacteristicCallbacks chrCallbacks;

void notifyTask(void * parameter){
    for(;;) {
        if(pServer->getConnectedCount()) {
            NimBLEService* pSvc = pServer->getServiceByUUID("BAAD");
            if(pSvc) {
                NimBLECharacteristic* pChr = pSvc->getCharacteristic("F00D");
                if(pChr) {
                    pChr->notify(true);
                }
            }
        }
        vTaskDelay(2000/portTICK_PERIOD_MS);
    }
    
    vTaskDelete(NULL);
}

void app_main(void) {
    printf("Starting NimBLE Server\n");

    /** sets device name */
    NimBLEDevice::init("NimBLE");

    /** Set the IO capabilities of the device, each option will trigger a different pairing method.
     *  BLE_HS_IO_DISPLAY_ONLY    - Passkey pairing
     *  BLE_HS_IO_DISPLAY_YESNO   - Numeric comparison pairing
     *  BLE_HS_IO_NO_INPUT_OUTPUT - DEFAULT setting - just works pairing
     */
    //NimBLEDevice::setSecurityIOCap(BLE_HS_IO_DISPLAY_ONLY); // use passkey
    //NimBLEDevice::setSecurityIOCap(BLE_HS_IO_DISPLAY_YESNO); //use numeric comparison

    /** 2 different ways to set security - both calls achieve the same result.
     *  no bonding, no man in the middle protection, secure connections.
     *   
     *  These are the default values, only shown here for demonstration.   
     */ 
    //NimBLEDevice::setSecurityAuth(false, false, true); 
    NimBLEDevice::setSecurityAuth(/*BLE_SM_PAIR_AUTHREQ_BOND | BLE_SM_PAIR_AUTHREQ_MITM |*/ BLE_SM_PAIR_AUTHREQ_SC);

    pServer = NimBLEDevice::createServer();
    pServer->setCallbacks(new ServerCallbacks());

    NimBLEService* pDeadService = pServer->createService("DEAD");
    NimBLECharacteristic* pBeefCharacteristic = pDeadService->createCharacteristic(
                                               "BEEF",
                                               NIMBLE_PROPERTY::READ |
                                               NIMBLE_PROPERTY::WRITE |
                               /** Require a secure connection for read and write access */
                                               NIMBLE_PROPERTY::READ_ENC |  // only allow reading if paired / encrypted
                                               NIMBLE_PROPERTY::WRITE_ENC   // only allow writing if paired / encrypted
                                              );
  
    pBeefCharacteristic->setValue("Burger");
    pBeefCharacteristic->setCallbacks(&chrCallbacks);

    /** 2902 and 2904 descriptors are a special case, when createDescriptor is called with
     *  either of those uuid's it will create the associated class with the correct properties
     *  and sizes. However we must cast the returned reference to the correct type as the method
     *  only returns a pointer to the base NimBLEDescriptor class.
     */
    NimBLE2904* pBeef2904 = (NimBLE2904*)pBeefCharacteristic->createDescriptor("2904"); 
    pBeef2904->setFormat(NimBLE2904::FORMAT_UTF8);
    pBeef2904->setCallbacks(&dscCallbacks);
  

    NimBLEService* pBaadService = pServer->createService("BAAD");
    NimBLECharacteristic* pFoodCharacteristic = pBaadService->createCharacteristic(
                                               "F00D",
                                               NIMBLE_PROPERTY::READ |
                                               NIMBLE_PROPERTY::WRITE |
                                               NIMBLE_PROPERTY::NOTIFY
                                              );

    pFoodCharacteristic->setValue("Fries");
    pFoodCharacteristic->setCallbacks(&chrCallbacks);

    /** Custom descriptor: Arguments are UUID, Properties, max length in bytes of the value */
    NimBLEDescriptor* pC01Ddsc = pFoodCharacteristic->createDescriptor(
                                               "C01D",
                                               NIMBLE_PROPERTY::READ | 
                                               NIMBLE_PROPERTY::WRITE|
                                               NIMBLE_PROPERTY::WRITE_ENC, // only allow writing if paired / encrypted
                                               20
                                              );
    pC01Ddsc->setValue("Send it back!");
    pC01Ddsc->setCallbacks(&dscCallbacks);

    /** Start the services when finished creating all Characteristics and Descriptors */  
    pDeadService->start();
    pBaadService->start();

    NimBLEAdvertising* pAdvertising = NimBLEDevice::getAdvertising();
    /** Add the services to the advertisment data **/
    pAdvertising->addServiceUUID(pDeadService->getUUID());
    pAdvertising->addServiceUUID(pBaadService->getUUID());
    /** If your device is battery powered you may consider setting scan response
     *  to false as it will extend battery life at the expense of less data sent.
     */
    pAdvertising->setScanResponse(true);
    pAdvertising->start();

    printf("Advertising Started\n");
    
    xTaskCreate(notifyTask, "notifyTask", 5000, NULL, 1, NULL);
}