示例：通过 WMI 接收事件通知

项目
07/03/2023

可以使用本主题中的过程和代码示例创建一个 WMI 客户端应用程序，用于执行 COM 初始化、连接到本地计算机上的 WMI、接收事件通知，然后进行清理。该示例在创建新进程时向用户通知某个事件。事件以异步方式接收。

以下过程用于执行 WMI 应用程序。步骤 1 到 5 包含设置和连接到 WMI 所需的所有步骤，步骤 6 是接收事件通知的位置。

通过 WMI 接收事件通知

通过调用 CoInitializeEx 初始化 COM 参数。

有关详细信息，请参阅初始化 WMI 应用程序的 COM。
通过调用 CoInitializeSecurity 初始化 COM 进程安全性。

有关详细信息，请参阅使用 C++ 设置默认进程安全级别。
通过调用 CoCreateInstance 获取 WMI 的初始定位符。

有关详细信息，请参阅创建到 WMI 命名空间的连接。
通过调用 IWbemLocator::ConnectServer，获取指向本地计算机上 root\cimv2 命名空间的 IWbemServices 的指针。若要连接到远程计算机，请参阅示例：从远程计算机获取 WMI 数据。

有关详细信息，请参阅创建到 WMI 命名空间的连接。
通过调用 CoSetProxyBlanket 设置 IWbemServices 代理安全性，以便 WMI 服务可以模拟客户端。

有关详细信息，请参阅在 WMI 连接上设置安全级别。
使用 IWbemServices 指针向 WMI 发出请求。此示例使用 IWbemServices::ExecNotificationQueryAsync 方法接收异步事件。收到异步事件时，必须提供 IWbemObjectSink 的实现。此示例提供 EventSink 类中的实现。主示例下面提供了此类的实现代码和头文件代码。每次收到事件时 IWbemServices::ExecNotificationQueryAsync 方法都会调用 EventSink::Indicate 方法。对于此示例，每次创建进程时，都会调用 EventSink::Indicate 方法。若要测试此示例，请运行代码并启动 Notepad.exe 等进程。这会触发事件通知。

若要详细了解如何发出 WMI 请求，请参阅操作类和实例信息以及调用方法。

以下示例代码通过 WMI 接收事件通知。

#include "eventsink.h"

int main(int iArgCnt, char ** argv)
{
    HRESULT hres;

    // Step 1: --------------------------------------------------
    // Initialize COM. ------------------------------------------

    hres =  CoInitializeEx(0, COINIT_MULTITHREADED); 
    if (FAILED(hres))
    {
        cout << "Failed to initialize COM library. Error code = 0x" 
             << hex << hres << endl;
        return 1;                  // Program has failed.
    }

    // Step 2: --------------------------------------------------
    // Set general COM security levels --------------------------

    hres =  CoInitializeSecurity(
        NULL, 
        -1,                          // COM negotiates service
        NULL,                        // Authentication services
        NULL,                        // Reserved
        RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication 
        RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation  
        NULL,                        // Authentication info
        EOAC_NONE,                   // Additional capabilities 
        NULL                         // Reserved
        );

                      
    if (FAILED(hres))
    {
        cout << "Failed to initialize security. Error code = 0x" 
             << hex << hres << endl;
        CoUninitialize();
        return 1;                      // Program has failed.
    }
    
    // Step 3: ---------------------------------------------------
    // Obtain the initial locator to WMI -------------------------

    IWbemLocator *pLoc = NULL;

    hres = CoCreateInstance(
        CLSID_WbemLocator,             
        0, 
        CLSCTX_INPROC_SERVER, 
        IID_IWbemLocator, (LPVOID *) &pLoc);
 
    if (FAILED(hres))
    {
        cout << "Failed to create IWbemLocator object. "
             << "Err code = 0x"
             << hex << hres << endl;
        CoUninitialize();
        return 1;                 // Program has failed.
    }

    // Step 4: ---------------------------------------------------
    // Connect to WMI through the IWbemLocator::ConnectServer method

    IWbemServices *pSvc = NULL;
 
    // Connect to the local root\cimv2 namespace
    // and obtain pointer pSvc to make IWbemServices calls.
    hres = pLoc->ConnectServer(
        _bstr_t(L"ROOT\\CIMV2"), 
        NULL,
        NULL, 
        0, 
        NULL, 
        0, 
        0, 
        &pSvc
    );
     
    if (FAILED(hres))
    {
        cout << "Could not connect. Error code = 0x" 
             << hex << hres << endl;
        pLoc->Release();     
        CoUninitialize();
        return 1;                // Program has failed.
    }

    cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;


    // Step 5: --------------------------------------------------
    // Set security levels on the proxy -------------------------

    hres = CoSetProxyBlanket(
        pSvc,                        // Indicates the proxy to set
        RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx 
        RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx 
        NULL,                        // Server principal name 
        RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx 
        RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
        NULL,                        // client identity
        EOAC_NONE                    // proxy capabilities 
    );

    if (FAILED(hres))
    {
        cout << "Could not set proxy blanket. Error code = 0x" 
             << hex << hres << endl;
        pSvc->Release();
        pLoc->Release();     
        CoUninitialize();
        return 1;               // Program has failed.
    }

    // Step 6: -------------------------------------------------
    // Receive event notifications -----------------------------

    // Use an unsecured apartment for security
    IUnsecuredApartment* pUnsecApp = NULL;

    hres = CoCreateInstance(CLSID_UnsecuredApartment, NULL, 
        CLSCTX_LOCAL_SERVER, IID_IUnsecuredApartment, 
        (void**)&pUnsecApp);
 
    EventSink* pSink = new EventSink;
    pSink->AddRef();

    IUnknown* pStubUnk = NULL; 
    pUnsecApp->CreateObjectStub(pSink, &pStubUnk);

    IWbemObjectSink* pStubSink = NULL;
    pStubUnk->QueryInterface(IID_IWbemObjectSink,
        (void **) &pStubSink);

    // The ExecNotificationQueryAsync method will call
    // The EventQuery::Indicate method when an event occurs
    hres = pSvc->ExecNotificationQueryAsync(
        _bstr_t("WQL"), 
        _bstr_t("SELECT * " 
            "FROM __InstanceCreationEvent WITHIN 1 "
            "WHERE TargetInstance ISA 'Win32_Process'"), 
        WBEM_FLAG_SEND_STATUS, 
        NULL, 
        pStubSink);

    // Check for errors.
    if (FAILED(hres))
    {
        printf("ExecNotificationQueryAsync failed "
            "with = 0x%X\n", hres);
        pSvc->Release();
        pLoc->Release();
        pUnsecApp->Release();
        pStubUnk->Release();
        pSink->Release();
        pStubSink->Release();
        CoUninitialize();    
        return 1;
    }

    // Wait for the event
    Sleep(10000);
         
    hres = pSvc->CancelAsyncCall(pStubSink);

    // Cleanup
    // ========

    pSvc->Release();
    pLoc->Release();
    pUnsecApp->Release();
    pStubUnk->Release();
    pSink->Release();
    pStubSink->Release();
    CoUninitialize();

    return 0;   // Program successfully completed.
 
}

以下头文件用于类 EventSink。在前面的代码示例中使用了 EventSink 类。

// EventSink.h
#ifndef EVENTSINK_H
#define EVENTSINK_H

#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>

#pragma comment(lib, "wbemuuid.lib")

class EventSink : public IWbemObjectSink
{
    LONG m_lRef;
    bool bDone;

public:
    EventSink() { m_lRef = 0; }
   ~EventSink() { bDone = true; }

    virtual ULONG STDMETHODCALLTYPE AddRef();
    virtual ULONG STDMETHODCALLTYPE Release();        
    virtual HRESULT 
        STDMETHODCALLTYPE QueryInterface(REFIID riid, void** ppv);

    virtual HRESULT STDMETHODCALLTYPE Indicate( 
            LONG lObjectCount,
            IWbemClassObject __RPC_FAR *__RPC_FAR *apObjArray
            );
        
    virtual HRESULT STDMETHODCALLTYPE SetStatus( 
            /* [in] */ LONG lFlags,
            /* [in] */ HRESULT hResult,
            /* [in] */ BSTR strParam,
            /* [in] */ IWbemClassObject __RPC_FAR *pObjParam
            );
};

#endif    // end of EventSink.h

以下示例代码是 EventSink 类的实现。

// EventSink.cpp
#include "eventsink.h"

ULONG EventSink::AddRef()
{
    return InterlockedIncrement(&m_lRef);
}

ULONG EventSink::Release()
{
    LONG lRef = InterlockedDecrement(&m_lRef);
    if(lRef == 0)
        delete this;
    return lRef;
}

HRESULT EventSink::QueryInterface(REFIID riid, void** ppv)
{
    if (riid == IID_IUnknown || riid == IID_IWbemObjectSink)
    {
        *ppv = (IWbemObjectSink *) this;
        AddRef();
        return WBEM_S_NO_ERROR;
    }
    else return E_NOINTERFACE;
}


HRESULT EventSink::Indicate(long lObjectCount,
    IWbemClassObject **apObjArray)
{
 HRESULT hres = S_OK;

    for (int i = 0; i < lObjectCount; i++)
    {
        printf("Event occurred\n");
    }

    return WBEM_S_NO_ERROR;
}

HRESULT EventSink::SetStatus(
            /* [in] */ LONG lFlags,
            /* [in] */ HRESULT hResult,
            /* [in] */ BSTR strParam,
            /* [in] */ IWbemClassObject __RPC_FAR *pObjParam
        )
{
    if(lFlags == WBEM_STATUS_COMPLETE)
    {
        printf("Call complete. hResult = 0x%X\n", hResult);
    }
    else if(lFlags == WBEM_STATUS_PROGRESS)
    {
        printf("Call in progress.\n");
    }

    return WBEM_S_NO_ERROR;
}    // end of EventSink.cpp

示例：通过 WMI 接收事件通知

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