尝试为Windows C++创建一个GATT客户端应用程序，该应用程序在建立连接时不会失败
我使用的是Windows APIGatt Client BLEfor C++，我的目标是连接两台设备(但在本例中我只尝试其中一台)，并保持不间断地读写数据，而不会在任何时候关闭设备。我的所有设备都有一个包含读特征和写特征的特定服务。
测试方法：
使用Visual Studio 2017(V141)和Windows SDK版本：10.0.18362.0，创建新的控制台(.exe)解决方案，在项目->；属性中将平台更改为Win32，然后转到项目->；属性->；C/C++->；命令行并添加以下选项：
/std:c++17 /await
然后将以下代码复制到一个文件中(您可以将所有代码复制到同一个.cpp文件中)：
#pragma once
#include <SDKDDKVer.h>
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <iostream>
#include <queue>
#include <map>
#include <mutex>
#include <condition_variable>
#include <string>
#include <winrt/Windows.Foundation.Collections.h>
#include <winrt/Windows.Web.Syndication.h>
#include "winrt/Windows.Devices.Bluetooth.h"
#include "winrt/Windows.Devices.Bluetooth.GenericAttributeProfile.h"
#include "winrt/Windows.Devices.Enumeration.h"
#include "winrt/Windows.Storage.Streams.h"
#pragma comment(lib, "windowsapp")
using namespace std;
using namespace winrt;
using namespace Windows::Foundation;
using namespace Windows::Foundation::Collections;
using namespace Windows::Web::Syndication;
using namespace Windows::Devices::Bluetooth;
using namespace Windows::Devices::Bluetooth::GenericAttributeProfile;
using namespace Windows::Devices::Enumeration;
using namespace Windows::Storage::Streams;
#pragma region STRUCS AND ENUMS
#define LOG_ERROR(e) cout << e << endl;
union to_guid
{
uint8_t buf[16];
guid guid;
};
const uint8_t BYTE_ORDER[] = { 3, 2, 1, 0, 5, 4, 7, 6, 8, 9, 10, 11, 12, 13, 14, 15 };
guid make_guid(const wchar_t* value)
{
to_guid to_guid;
memset(&to_guid, 0, sizeof(to_guid));
int offset = 0;
for (unsigned int i = 0; i < wcslen(value); i++) {
if (value[i] >= '0' && value[i] <= '9')
{
uint8_t digit = value[i] - '0';
to_guid.buf[BYTE_ORDER[offset / 2]] += offset % 2 == 0 ? digit << 4 : digit;
offset++;
}
else if (value[i] >= 'A' && value[i] <= 'F')
{
uint8_t digit = 10 + value[i] - 'A';
to_guid.buf[BYTE_ORDER[offset / 2]] += offset % 2 == 0 ? digit << 4 : digit;
offset++;
}
else if (value[i] >= 'a' && value[i] <= 'f')
{
uint8_t digit = 10 + value[i] - 'a';
to_guid.buf[BYTE_ORDER[offset / 2]] += offset % 2 == 0 ? digit << 4 : digit;
offset++;
}
else
{
// skip char
}
}
return to_guid.guid;
}
mutex subscribeLock;
condition_variable subscribeSignal;
mutex _mutexWrite;
condition_variable signalWrite;
struct DeviceCacheEntry {
BluetoothLEDevice device = nullptr;
GattDeviceService service = nullptr;
GattCharacteristic characteristic = nullptr;
};
map<wstring, DeviceCacheEntry> cache;
struct Subscription {
GattCharacteristic::ValueChanged_revoker revoker;
};
struct BLEDeviceData {
wstring id;
wstring name;
bool isConnectable = false;
Subscription* subscription = NULL;
};
vector<BLEDeviceData> deviceList{};
mutex deviceListLock;
condition_variable deviceListSignal;
#pragma endregion
#pragma region CACHE FUNCTIONS
//Call this function to get a device from cache or async if it wasn't found
IAsyncOperation<BluetoothLEDevice> getDevice(wchar_t* deviceId) {
if (cache.count(wstring(deviceId)) && cache[wstring(deviceId)].device)
co_return cache[wstring(deviceId)].device;
BluetoothLEDevice result = co_await BluetoothLEDevice::FromIdAsync(deviceId);
if (result == nullptr) {
LOG_ERROR("Failed to connect to device.")
co_return nullptr;
}
else {
DeviceCacheEntry d;
d.device = result;
if (!cache.count(wstring(deviceId))) {
cache.insert({ wstring(deviceId), d });
}
else {
cache[wstring(deviceId)] = d;
}
co_return cache[wstring(deviceId)].device;
}
}
//Call this function to get a service from cache or async if it wasn't found
IAsyncOperation<GattDeviceService> getService(wchar_t* deviceId, wchar_t* serviceId) {
if (cache.count(wstring(deviceId)) && cache[wstring(deviceId)].service)
co_return cache[wstring(deviceId)].service;
auto device = co_await getDevice(deviceId);
if (device == nullptr)
co_return nullptr;
GattDeviceServicesResult result = co_await device.GetGattServicesForUuidAsync(make_guid(serviceId), BluetoothCacheMode::Cached);
if (result.Status() != GattCommunicationStatus::Success) {
LOG_ERROR("Failed getting services. Status: " << (int)result.Status())
co_return nullptr;
}
else if (result.Services().Size() == 0) {
LOG_ERROR("No service found with uuid")
co_return nullptr;
}
else {
if (cache.count(wstring(deviceId))) {
cache[wstring(deviceId)].service = result.Services().GetAt(0);
}
co_return cache[wstring(deviceId)].service;
}
}
//Call this function to get a characteristic from cache or async if it wasn't found
IAsyncOperation<GattCharacteristic> getCharacteristic(wchar_t* deviceId, wchar_t* serviceId, wchar_t* characteristicId) {
try {
if (cache.count(wstring(deviceId)) && cache[wstring(deviceId)].characteristic)
co_return cache[wstring(deviceId)].characteristic;
auto service = co_await getService(deviceId, serviceId);
if (service == nullptr)
co_return nullptr;
GattCharacteristicsResult result = co_await service.GetCharacteristicsForUuidAsync(make_guid(characteristicId), BluetoothCacheMode::Cached);
if (result.Status() != GattCommunicationStatus::Success) {
LOG_ERROR("Error scanning characteristics from service. Status: " << (int)result.Status())
co_return nullptr;
}
else if (result.Characteristics().Size() == 0) {
LOG_ERROR("No characteristic found with uuid")
co_return nullptr;
}
else {
if (cache.count(wstring(deviceId))) {
cache[wstring(deviceId)].characteristic = result.Characteristics().GetAt(0);
}
co_return cache[wstring(deviceId)].characteristic;
}
}
catch (...) {
LOG_ERROR("Exception while trying to get characteristic")
}
}
#pragma endregion
#pragma region SCAN DEVICES FUNCTIONS
DeviceWatcher deviceWatcher{ nullptr };
mutex deviceWatcherLock;
DeviceWatcher::Added_revoker deviceWatcherAddedRevoker;
DeviceWatcher::Updated_revoker deviceWatcherUpdatedRevoker;
DeviceWatcher::Removed_revoker deviceWatcherRemovedRevoker;
DeviceWatcher::EnumerationCompleted_revoker deviceWatcherCompletedRevoker;
struct TestBLE {
static void ScanDevices();
static void StopDeviceScan();
};
//This function would be called when a new BLE device is detected
void DeviceWatcher_Added(DeviceWatcher sender, DeviceInformation deviceInfo) {
BLEDeviceData deviceData;
deviceData.id = wstring(deviceInfo.Id().c_str());
deviceData.name = wstring(deviceInfo.Name().c_str());
if (deviceInfo.Properties().HasKey(L"System.Devices.Aep.Bluetooth.Le.IsConnectable")) {
deviceData.isConnectable = unbox_value<bool>(deviceInfo.Properties().Lookup(L"System.Devices.Aep.Bluetooth.Le.IsConnectable"));
}
deviceList.push_back(deviceData);
}
//This function would be called when an existing BLE device is updated
void DeviceWatcher_Updated(DeviceWatcher sender, DeviceInformationUpdate deviceInfoUpdate) {
wstring deviceData = wstring(deviceInfoUpdate.Id().c_str());
for (int i = 0; i < deviceList.size(); i++) {
if (deviceList[i].id == deviceData) {
if (deviceInfoUpdate.Properties().HasKey(L"System.Devices.Aep.Bluetooth.Le.IsConnectable")) {
deviceList[i].isConnectable = unbox_value<bool>(deviceInfoUpdate.Properties().Lookup(L"System.Devices.Aep.Bluetooth.Le.IsConnectable"));
}
break;
}
}
}
void DeviceWatcher_Removed(DeviceWatcher sender, DeviceInformationUpdate deviceInfoUpdate) {
}
void DeviceWatcher_EnumerationCompleted(DeviceWatcher sender, IInspectable const&) {
TestBLE::StopDeviceScan();
TestBLE::ScanDevices();
}
//Call this function to scan async all BLE devices
void TestBLE::ScanDevices() {
try {
lock_guard lock(deviceWatcherLock);
IVector<hstring> requestedProperties = single_threaded_vector<hstring>({ L"System.Devices.Aep.DeviceAddress", L"System.Devices.Aep.IsConnected", L"System.Devices.Aep.Bluetooth.Le.IsConnectable" });
hstring aqsFilter = L"(System.Devices.Aep.ProtocolId:="{bb7bb05e-5972-42b5-94fc-76eaa7084d49}")"; // list Bluetooth LE devices
deviceWatcher = DeviceInformation::CreateWatcher(aqsFilter, requestedProperties, DeviceInformationKind::AssociationEndpoint);
deviceWatcherAddedRevoker = deviceWatcher.Added(auto_revoke, &DeviceWatcher_Added);
deviceWatcherUpdatedRevoker = deviceWatcher.Updated(auto_revoke, &DeviceWatcher_Updated);
deviceWatcherRemovedRevoker = deviceWatcher.Removed(auto_revoke, &DeviceWatcher_Removed);
deviceWatcherCompletedRevoker = deviceWatcher.EnumerationCompleted(auto_revoke, &DeviceWatcher_EnumerationCompleted);
deviceWatcher.Start();
}
catch (exception e) {
LOG_ERROR(e.what())
}
}
void TestBLE::StopDeviceScan() {
scoped_lock lock(deviceListLock, deviceWatcherLock);
if (deviceWatcher != nullptr) {
deviceWatcherAddedRevoker.revoke();
deviceWatcherUpdatedRevoker.revoke();
deviceWatcherRemovedRevoker.revoke();
deviceWatcherCompletedRevoker.revoke();
deviceWatcher.Stop();
deviceWatcher = nullptr;
}
deviceListSignal.notify_one();
}
#pragma endregion
#pragma region SUBSCRIBE/READ FUNCTIONS
//On this function you can read all data from the specified characteristic
void Characteristic_ValueChanged(GattCharacteristic const& characteristic, GattValueChangedEventArgs args)
{
LOG_ERROR("Read data from device: " << to_string(characteristic.Service().Device().DeviceId()) << ", data size: " << args.CharacteristicValue().Length())
}
//Function used to subscribe async to the specific device
fire_and_forget SubscribeCharacteristicAsync(wstring deviceId, wstring serviceId, wstring characteristicId, bool* result) {
try {
auto characteristic = co_await getCharacteristic(&deviceId[0], &serviceId[0], &characteristicId[0]);
if (characteristic != nullptr) {
auto status = co_await characteristic.WriteClientCharacteristicConfigurationDescriptorAsync(GattClientCharacteristicConfigurationDescriptorValue::Notify);
if (status != GattCommunicationStatus::Success) {
LOG_ERROR("Error subscribing to characteristic. Status: " << (int)status)
}
else {
for (int i = 0; i < deviceList.size(); i++) {
if (deviceList[i].id == deviceId) {
deviceList[i].subscription = new Subscription();
deviceList[i].subscription->revoker = characteristic.ValueChanged(auto_revoke, &Characteristic_ValueChanged);
break;
}
}
if (result != 0)
*result = true;
}
}
}
catch (hresult_error& ex)
{
LOG_ERROR("SubscribeCharacteristicAsync error: " << to_string(ex.message().c_str()))
for (int i = 0; i < deviceList.size(); i++) {
if (deviceList[i].id == deviceId && deviceList[i].subscription) {
delete deviceList[i].subscription;
deviceList[i].subscription = NULL;
break;
}
}
}
subscribeSignal.notify_one();
}
//Call this function to subscribe to the specific device so you can read data from it
bool SubscribeCharacteristic(wstring deviceId, wstring serviceId, wstring characteristicId) {
unique_lock<mutex> lock(subscribeLock);
bool result = false;
SubscribeCharacteristicAsync(deviceId, serviceId, characteristicId, &result);
subscribeSignal.wait(lock);
return result;
}
#pragma endregion
#pragma region WRITE FUNCTIONS
//Function used to send data async to the specific device
fire_and_forget SendDataAsync(wchar_t* deviceId, wchar_t* serviceId, wchar_t* characteristicId, uint8_t * data, uint16_t size, bool* result) {
try {
auto characteristic = co_await getCharacteristic(deviceId, serviceId, characteristicId);
if (characteristic != nullptr) {
DataWriter writer;
writer.WriteBytes(array_view<uint8_t const>(data, data + size));
IBuffer buffer = writer.DetachBuffer();
auto status = co_await characteristic.WriteValueAsync(buffer, GattWriteOption::WriteWithoutResponse);
if (status != GattCommunicationStatus::Success) {
LOG_ERROR("Error writing value to characteristic. Status: " << (int)status)
}
else if (result != 0) {
LOG_ERROR("Data written succesfully")
*result = true;
}
}
}
catch (hresult_error& ex)
{
LOG_ERROR("SendDataAsync error: " << to_string(ex.message().c_str()))
for (int i = 0; i < deviceList.size(); i++) {
if (deviceList[i].id == deviceId && deviceList[i].subscription) {
delete deviceList[i].subscription;
deviceList[i].subscription = NULL;
break;
}
}
}
signalWrite.notify_one();
}
//Call this function to write data on the device
bool SendData(wchar_t* deviceId, wchar_t* serviceId, wchar_t* characteristicId, uint8_t * data, uint16_t size) {
bool result = false;
unique_lock<mutex> lock(_mutexWrite);
// copy data to stack so that caller can free its memory in non-blocking mode
SendDataAsync(deviceId, serviceId, characteristicId, data, size, &result);
signalWrite.wait(lock);
return result;
}
#pragma endregion
最后复制此主函数(可以在同一文件末尾复制)：
int main() {
//The mac of the device that will be tested
wstring deviceMac = L"00:11:22:33:44:55";
//These are the serviceUUID, readCharacteristicUUID and writeCharacteristicUUID as I said previously
wstring serviceUUID = L"{47918888-5555-2222-1111-000000000000}";
wstring readUUID = L"{31a28888-5555-2222-1111-00000000cede}";
wstring writeUUID = L"{f55a8888-5555-222-1111-00000000957a}";
//I think it is the mac of the BLE USB Dongle because it is in all device id when they are enumerated
wstring otherMac = L"24:4b:fe:3a:1a:ba";
//The device Id that we are looking for
wstring deviceId = L"BluetoothLE#BluetoothLE" + otherMac;
deviceId += L"-";
deviceId += deviceMac;
//To start scanning just call this function
TestBLE::ScanDevices();
//Data to be written all the time
const uint16_t dataSize = 3;
uint8_t data [dataSize]= { 0x0, 0xff, 0xff };
//Wait time in miliseconds between each write
chrono::milliseconds waitTime = 100ms;
//It will be executed always
while (true) {
//Then every device and their info updated would be in this vector
for (int i = 0; i < deviceList.size(); i++) {
//If the device is connectable we will try to connect if we aren't subscribed yet or send information
if (deviceList[i].isConnectable) {
//We can do here the following code to know the structure of the device id (if otherMac variable is the BLE USB dongle mac or not)
//cout << to_string(deviceList[i].id) << endl;
if (!deviceList[i].subscription && deviceList[i].id == deviceId) {
SubscribeCharacteristic(deviceList[i].id, serviceUUID, readUUID);
}
else if (deviceList[i].subscription) {
SendData(&deviceId[0], &serviceUUID[0], &writeUUID[0], data, dataSize);
}
}
}
this_thread::sleep_for(waitTime);
}
}
您将需要具有包含读取和写入特征的服务的BLE设备，请在deviceMac、serviceUUID、readUUID和writeUUID变量中设置相应值??，您还可以修改要写入data和dataSize变量中的字节数，以及写入间隔时间其他Mac变量应该是BLE USB加密狗设备的MAC，但我建议您通过从for循环内的deviceList获取设备ID来检查它。
当您在极少数情况下运行此代码时，您将收到错误"；Failed geting services。状态："；，结果为1(无法访问)或3(访问被拒绝)，在睡觉的情况下，它将正确读取设备数据，一段时间后它将给出错误&Quot；SendDataAsync Error：对象已释放&qot；，并将从那里继续给出"；SubscribeCharacteristic异步错误：对象已释放(&em>"；SubscribeCharacteristic Async错误：对象已释放可能的原因是什么？编辑1： 这非常奇怪，因为使用此代码时，数据从未正确写入(&q；数据已成功写入消息不显示)，但在我完成的代码中，我始终能够写入数据，可能问题仍然是一样的，它与&q；map<；wstring，DeviceCacheEntry&>高速缓存&q；中存储的特征有关(&q；映射<；wstring，DeviceCacheEntry&>缓存&q；中存储的特征)。因为它可能存储为副本，并且在某个时候尝试访问它时，Windows会处理(因为它是存储在缓存中的原始副本)，并在名为"；update 2-某些怪异&
的位置给出错误，如this post的答案中所述解决方案
如下面的链接所述，BLEE设备不会建立长期配对。它们连接的时间足够长以交换数据，然后断开连接以收听广播和公告。
https://social.msdn.microsoft.com/Forums/vstudio/en-US/5fdff026-3732-4bd2-b57e-fbeb5ab721c8/bluetooth-le-winrt-c-code-works-if-device-not-paired-fails-with-unreachable-if-device-is-paired?forum=wdk
因此，您需要做的就是使代码再次连接到设备，而不会丢失该过程。
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