How to check if a container supports multiple connections?

Question

• Implemented the Sink Class - to receive event notifications from COM Server
• Event Interface derives from IDispatch

I have an issue whereby an IConnectionPoint::Advise call returns E_NOTIMPL. This could be because the connection point only allows one connection - MSDN.

Note:

• COM Server is out-of-process
• Pure C++ implementation

EDIT:

S8.tlh: C++ source equivalent of Win32 type library S8.tlb:

struct __declspec(uuid("090910c3-28c3-45fe-861d-edcf11aa9788"))
IS8SimulationEvents : IDispatch
{

    // Methods:
    HRESULT S8SimulationReset ( );
    HRESULT S8SimulationEndRun ( );
    HRESULT S8SimulationCustomEvent (
        BSTR * TextInfo );
    HRESULT S8SimulationOpened ( );
    HRESULT S8SimulationEndTrial ( );
    HRESULT S8SimulationOEMEvent (
        BSTR * TextInfo );
    HRESULT S8SimulationReadyToClose ( );
    HRESULT S8SimulationUserMessage (
        long * Answer,
        BSTR * TextMsg,
        long ValidAnswers );
};

Implementation of Class Sink - to handle event notifications:

class Sink : public IS8SimulationEvents
{
public:
Sink(){
    m_dwRefCount = 0;
};
~Sink(){};
/*
* IS8SimulationEvent interface functions
*/
HRESULT S8SimulationEndTrial()
{
    cout << "Simulation complete." << endl;
    return S_OK;;
};

HRESULT S8SimulationOpened()
{
    cout << "Simulation open." << endl;
    return S_OK;
};

HRESULT S8SimulationReadyToClose()
{
    cout << "Simulation ready to close" << endl;
    return S_OK;
};

ULONG STDMETHODCALLTYPE AddRef()
{
    m_dwRefCount++;
    return m_dwRefCount;
};

ULONG STDMETHODCALLTYPE Release()
{
    ULONG l;
    l = m_dwRefCount--;

    if (0 == m_dwRefCount)
    {
        delete this;
    }

    return m_dwRefCount;
};

HRESULT STDMETHODCALLTYPE QueryInterface(
                                        REFIID iid ,
                                        void **ppvObject)
{
    m_dwRefCount++;
    *ppvObject = (void *)this;
    return S_OK;
};

HRESULT STDMETHODCALLTYPE GetTypeInfoCount(UINT *pctinfo)
{
    return E_NOTIMPL;
};

HRESULT STDMETHODCALLTYPE GetIDsOfNames( 
                                        REFIID riid,
                                        LPOLESTR *rgszNames,
                                        UINT cNames,
                                        LCID lcid,
                                        DISPID *rgDispId)
{
    return E_NOTIMPL;
};

HRESULT STDMETHODCALLTYPE GetTypeInfo(
                                    unsigned int iTInfo,
                                    LCID lcid,
                                    ITypeInfo FAR* FAR* ppTInfo)
{
    return E_NOTIMPL;
};

HRESULT STDMETHODCALLTYPE Invoke(
                                DISPID dispIdMember,
                                REFIID riid,
                                LCID lcid,
                                WORD wFlags,
                                DISPPARAMS FAR* pDispParams,
                                VARIANT FAR* pVarResult,
                                EXCEPINFO FAR* pExcepInfo,
                                unsigned int FAR* puArgErr)
{
    HRESULT hresult = S_OK;
    if (pDispParams)
    {
        switch (dispIdMember) {
        case 1:
            return S8SimulationEndTrial();
        case 2:
            return S8SimulationOpened();
        case 3:
            return S8SimulationReadyToClose();
        default:
            return E_NOTIMPL;
        }

    }
    return E_NOTIMPL;
}
private:
    DWORD m_dwRefCount;
public:
void SetupConnectionPoint (IS8Simulation *pis8)
{

    HRESULT hresult;
    IConnectionPointContainer *pContainer = NULL;
    IConnectionPoint *pConnection = NULL;
    IUnknown *pSinkUnk = NULL;
    Sink *pSink = NULL;
    DWORD dwAdvise;

    dwAdvise = 0;

    hresult = pis8->QueryInterface(
                        __uuidof(IConnectionPointContainer),
                        (void **) &pContainer);

    if (SUCCEEDED(hresult))
    {
        cout << "IConnectionPointContainer inteface supported." << endl;
    } else {
        cerr << "Error: No such interface supported." << endl;
        exit (hresult);
    }

                                    __uuidof(IS8SimulationEvents),
                                    &pConnection); 

    switch (HRESULT_CODE(hresult)) {
        case NOERROR:
            cout << "Obtained valid interface pointer." << endl;
            break;
        case E_POINTER:
            cerr << "Invalid pointer: the address is not valid." << endl;
            exit (hresult);
            break;
        case CONNECT_E_NOCONNECTION:
            cerr << "This connectable object not support the "
                    "outgoing interface specified." << endl;
            exit (hresult);
            break;
        case E_UNEXPECTED:
        default:
            cerr << "Catastrophic failure." << endl;
            exit (hresult);
            break;
    }

    pContainer->Release();


    hresult = pSink->QueryInterface(
                            __uuidof(IUnknown),
                            (void **)&pSinkUnk);

    if (FAILED(hresult))
    {
        exit (EXIT_FAILURE);
    }

    hresult = pConnection->Advise(
                            pSinkUnk,
                            &dwAdvise);

    switch (HRESULT_CODE(hresult)) {
        case NOERROR:
            cout << "The connection has been established and "
                    "*dwAdvise has the connection token." << endl;
            break;
        case E_POINTER:
            cerr << "Invalid pointer: "
                    "the value pSinkUnk or dwAdvise is not valid." << endl;
            exit (hresult);
            break;
        case CONNECT_E_ADVISELIMIT:
            cerr << "The connection point has already reached "
                    "its limit of connections and cannot accept "
                    "any more." << endl;
            exit (hresult);
            break;
        case CONNECT_E_CANNOTCONNECT:
            cerr << "The sink does not support the interface "
                    "required by this connection point." << endl;
            exit (hresult);
            break;
        case E_NOTIMPL:
            break;
            case E_UNEXPECTED:
            default:
        cerr << "Catastrophic failure." << endl;
        exit (hresult);
        break;
    }
    return;
}
};

EDIT:

Implementation of IUnknown Interface in Sink Class

ULONG STDMETHODCALLTYPE AddRef()
{
    m_dwRefCount++;
    return m_dwRefCount;
};

ULONG STDMETHODCALLTYPE Release()
{
    ULONG l;
    l = m_dwRefCount--;

    if (0 == m_dwRefCount)
    {
        delete this;
    }

    return m_dwRefCount;
};

HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void **ppvObject)
{
    m_dwRefCount++;
    *ppvObject = (void *)this;
    return S_OK;
};

Question:

• How to check if a container supports multiple connections?
• If more information is required, please comment accordingly.

Answer 1

Solved:

• Using pure C++
• No ATL

With the following implementation of QI:

HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void **ppvObject)
{
    if (iid == __uuidof(IUnknown) || iid == __uuidof(IS8SimulationEvents))
    {
        *ppvObject = (IS8SimulationEvents*)this;
    } else {
        *ppvObject = NULL;
        return E_NOINTERFACE;
    }
    m_dwRefCount++;
    return S_OK;
};

Answer 2

Please read the MSDN article again.

 A connection point that allows only one interface
 can return E_NOTIMPL FROM the IConnectionPoint::EnumConnections method
EnumConnections : E_NOTIMPL 
The connection point does not support enumeration.

IConnectionPoint::Advise is required to reply

CONNECT_E_ADVISELIMIT

when he connection point has already reached its limit of connections and cannot accept any more.

--

Michael

Answer 3

AtlAdvise should cause the connectionpoint to call QI on the event sink. You cannot be sure WHAT or how many times it might call QI.

Suggestion: Refer to something like this in the eventsink to determine the correct event interface is queried.

void GuidToString(PTCHAR s, LPGUID piid )
{
_stprintf(s, _T("{%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x}"),
    piid->Data1, piid->Data2,
    piid->Data3,
    piid->Data4[0], piid->Data4[1],
    piid->Data4[2], piid->Data4[3],
    piid->Data4[4], piid->Data4[5],
    piid->Data4[6], piid->Data4[7]);
    // Outputdebugstr (s)
}

ALSO the event sink QueryInterface should do something like

if (iid == IID_IUnknown || iid == IID_AppEvents)
     *ppObj = (AppEvents*)this;

So it returns only the correct interface.

Answer 4

COM Library calls QI for so many interfaces like IUnknown, IMarshall etc when Advise call in invoked.

As Michael pointed about the MSDN article, it says that it returns E_NOTIMPL only for EnumConnections API and not for Advise. I suspect QI for returning the E_NOTIMPL. So try to trace the Advise API. And you will come to know about the failure of QI.