PRB: Serialization with CSocketFile and CArchive Might Stop in a Multiprocessor Environment

• The Microsoft Foundation Classes (MFC)
• Microsoft Visual C++, 32-bit Editions, versions 2.1, 2.2, 4.0, 4.1, 4.2, 5.0, 6.0

SYMPTOMS

When you are doing serialization with the MFC CSocketFile and CArchive classes in a multiprocessor environment, an application may stop (hang) while it is waiting for data to be received.

CAUSE

The following are possible causes:

• The read-ahead behavior described by the following Microsoft Knowledge Base article might cause the missing of FD_READ notification from the lower Winsock layer:




Q192704 PRB: CArchive::Read Might Hang When Using CSocketFile

• The IOCtl(FIONREAD, &nBytes) call inside the CAsyncSocket::DoCallBack class implementation of the Sockcore.cpp file in the MFC source might also be subject to possible error, because of the report of incorrect data count, as described by the following Microsoft Knowledge Base article:

Q192599 INFO: Avoid Data Peeking in Winsock

RESOLUTION

Avoid using serialization in network programming. For additional information and guidelines, click the article numbers below to view the articles in the Microsoft Knowledge Base:

Q185728 SAMPLE: MFCSocs.exe Avoids Two Common MFC Socket Mistakes

Q192570 MFCAsync: Message-Oriented TCP and Multithreaded Client/Server

1. On the Project menu, click Settings, and then click the General tab. Under the Microsoft Foundation Classes box, click Use MFC in a Static Library. Click the Link tab, click Customize in the Category box, and then click Force File output.



2. Append the following to your StdAfx.cpp file:

   
   void PASCAL CAsyncSocket::DoCallBack(WPARAM wParam, LPARAM lParam)
   {
       if (wParam == 0 && lParam == 0)
           return;
   
       // Has the socket been closed?
       CAsyncSocket* pSocket = CAsyncSocket::LookupHandle((SOCKET)wParam, TRUE);
   
       // If yes, ignore message.
       if (pSocket != NULL)
           return;
   
       pSocket = CAsyncSocket::LookupHandle((SOCKET)wParam, FALSE);
       if (pSocket == NULL)
       {
           // Must be in the middle of an Accept call.
           pSocket = CAsyncSocket::LookupHandle(INVALID_SOCKET, FALSE);
           ASSERT(pSocket != NULL);
           pSocket->m_hSocket = (SOCKET)wParam;
           CAsyncSocket::DetachHandle(INVALID_SOCKET, FALSE);
           CAsyncSocket::AttachHandle(pSocket->m_hSocket, pSocket, FALSE);
       }
   
       int nErrorCode = WSAGETSELECTERROR(lParam);
       switch (WSAGETSELECTEVENT(lParam))
       {
       case FD_READ:
           {   // Comment out the data peeking code here
               //DWORD nBytes;
               //if (!pSocket->IOCtl(FIONREAD, &nBytes))
               //  nErrorCode = WSAGetLastError();
               //if (nBytes != 0 || nErrorCode != 0)
                   pSocket->OnReceive(nErrorCode);
           }
           break;
       case FD_WRITE:
           pSocket->OnSend(nErrorCode);
           break;
       case FD_OOB:
           pSocket->OnOutOfBandData(nErrorCode);
           break;
       case FD_ACCEPT:
           pSocket->OnAccept(nErrorCode);
           break;
       case FD_CONNECT:
           pSocket->OnConnect(nErrorCode);
           break;
       case FD_CLOSE:
           pSocket->OnClose(nErrorCode);
           break;
       }
   } 

STATUS

This behavior is by design.

Additional query words: CSocket CAsyncSocket

Keywords : kbnetwork kbAPI kbSDKPlatform kbWinsock kbGrpNet
Version : winnt:2.1,2.2,4.0,4.1,4.2,5.0,6.0
Platform : winnt
Issue type : kbprb