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

Hi Atkin. 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 2

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.

Answer 3

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;
};