Searching Asynchronously in C++

The following code can be used as a basis for a C++ application that searches for devices asynchronously. The code implements the IUPnPDeviceFinderCallback interface by creating a class that inherits from it.

To implement both IUPnPDeviceFinderCallback and IUPnPDeviceFinderAddCallbackWithInterface, the class must inherit from both interfaces. Implementation of IUPnPDeviceFinderAddCallbackWithInterface is optional, but if you choose to implement it, you must also implement IUPnPDeviceFinderCallback.


#include <windows.h>
#include <upnp.h>
#include <stdio.h>

#pragma comment(lib, "ole32.lib")
#pragma comment(lib, "oleaut32.lib")
#pragma comment(lib, "user32.lib")

class CUPnPDeviceFinderCallback : public IUPnPDeviceFinderCallback
{
public:
    CUPnPDeviceFinderCallback()
    {
        m_lRefCount = 0;
    };
    
    STDMETHODIMP QueryInterface(REFIID iid, LPVOID* ppvObject)
    {
        HRESULT hr = S_OK;
        
        if(NULL == ppvObject)
        {
            hr = E_POINTER;
        }
        else
        {
            *ppvObject = NULL;
        }
        
        if(SUCCEEDED(hr))
        {
            if(IsEqualIID(iid, IID_IUnknown) || IsEqualIID(iid, IID_IUPnPDeviceFinderCallback))
            {
                *ppvObject = static_cast<IUPnPDeviceFinderCallback*>(this);
                AddRef();
            }
            else
            {
                hr = E_NOINTERFACE;
            }
        }
        
        return hr;
    };
    
    STDMETHODIMP_(ULONG) AddRef()
    {
        return ::InterlockedIncrement(&m_lRefCount);
    };
    
    STDMETHODIMP_(ULONG) Release()
    {
        LONG lRefCount = ::InterlockedDecrement(&m_lRefCount);
        if(0 == lRefCount)
        {
            delete this;
        }
        
        return lRefCount;
    };
    
    STDMETHODIMP DeviceAdded(LONG lFindData, IUPnPDevice* pDevice)
    {
        HRESULT hr = S_OK;

        //You should save pDevice so that it is accessible outside the scope of this method.

        BSTR UniqueDeviceName;
        hr = pDevice->get_UniqueDeviceName(&UniqueDeviceName);
        if (SUCCEEDED(hr))
        {
            BSTR FriendlyName;
            hr = pDevice->get_FriendlyName(&FriendlyName);
            if (SUCCEEDED(hr))
            {
                printf("Device Added: udn: %S, name: %S\n", FriendlyName, UniqueDeviceName);
                ::SysFreeString(FriendlyName);
            }
            ::SysFreeString(UniqueDeviceName);
        }
        return hr;
        
    };
    
    STDMETHODIMP DeviceRemoved(LONG lFindData, BSTR bstrUDN)
    {
        printf("Device Removed: udn: %S", bstrUDN);
        return S_OK;
    };
    
    STDMETHODIMP SearchComplete(LONG lFindData)
    {
        return S_OK;
    };
    
    
    
private:
    LONG m_lRefCount;
    
};

HRESULT FindUPnPDevice(BSTR TypeURI)
{
    HRESULT hr = S_OK;
    
    IUPnPDeviceFinderCallback* pUPnPDeviceFinderCallback = new CUPnPDeviceFinderCallback();
    if(NULL != pUPnPDeviceFinderCallback)
    {
        pUPnPDeviceFinderCallback->AddRef();
        IUPnPDeviceFinder* pUPnPDeviceFinder;
        hr = CoCreateInstance(CLSID_UPnPDeviceFinder, NULL, CLSCTX_INPROC_SERVER, 
            IID_IUPnPDeviceFinder, reinterpret_cast<void**>(&pUPnPDeviceFinder));
        if(SUCCEEDED(hr))
        {
            LONG lFindData;
            hr = pUPnPDeviceFinder->CreateAsyncFind(TypeURI, 0, pUPnPDeviceFinderCallback, &lFindData);
            if(SUCCEEDED(hr))
            {
                hr = pUPnPDeviceFinder->StartAsyncFind(lFindData);
                if(SUCCEEDED(hr))
                {
                    // STA threads must pump messages
                    MSG Message;
                    BOOL bGetMessage;
                    while(bGetMessage = GetMessage(&Message, NULL, 0, 0) && -1 != bGetMessage)
                    {
                        DispatchMessage(&Message);      
                    }
                }
                pUPnPDeviceFinder->CancelAsyncFind(lFindData);
            }
            pUPnPDeviceFinder->Release();
        }
        pUPnPDeviceFinderCallback->Release();
    }
    else
    {
        hr = E_OUTOFMEMORY;
    }
   
    return hr;
}


 

 

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