231 - All pipe instances are busy when connecting a pipe

From:
"Bill Holt" <mailbill(NOSPAM)@21cn.com.nospam>
Newsgroups:
microsoft.public.vc.mfc,microsoft.public.win32.programmer.kernel
Date:
Mon, 29 Sep 2008 11:37:48 +0800
Message-ID:
<07EBF019-2108-48B0-86B6-9BD5FBB8BC0D@microsoft.com>
Hi,

I'm working on a pipe server & client program. The pipe server is
asynchronous and multithreaded. I used the following method to create the
server:

// code below is inside the Run() method of the server thread class
OVERLAPPED ol;
ZeroMemory(&ol, sizeof(OVERLAPPED));
HANDLE hArray[2];
hArray[0] = ol.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
hArray[1] = m_hStopEvent; // a global shutdown event
while(bStop==FALSE)
{
    HANDLE hServerPipe = CreateNamedPipe (m_szServerName,
PIPE_ACCESS_DUPLEX|FILE_FLAG_OVERLAPPED|WRITE_DAC,PIPE_TYPE_MESSAGE |
PIPE_READMODE_MESSAGE | PIPE_WAIT, PIPE_UNLIMITED_INSTANCES, 8192, 8192,
NMPWAIT_USE_DEFAULT_WAIT, &saPipeSecurity);
    if (hServerPipe && hServerPipe != INVALID_HANDLE_VALUE)
    {
        BOOL bClientConnected = ConnectNamedPipe(hServerPipe, &ol);
        switch (WaitForMultipleObjects(2, hArray, FALSE, INFINITE))
        {
        case WAIT_OBJECT_0:
            if (GetOverlappedResult(hServerPipe, &ol, &dwOverlappedBytes,
TRUE))
            {
                // calling _beginthreadex & CloseHandle here to process
requests
            }
            break;
        case WAIT_OBJECT_0+1:
            // shut down server
            bStop=TRUE;
            CloseHandle(hServerPipe);
            break;
        }
    }
}

The _beginthreadex part isn't that complicated. It passes hServerPipe as a
parameter so that the created thread can process it. The client code is as
below:

// code below is inside a client thread
// the client launches multiple threads to send requests to the server
HANDLE hPipe = CreateFile(m_szServerName, GENERIC_READ|GENERIC_WRITE,0,NULL,
OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
if(hPipe && hPipe != INVALID_HANDLE_VALUE)
{
    OVERLAPPED ol;
    ZeroMemory(&ol, sizeof(OVERLAPPED));
    ol.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    BOOL bResult = WriteFile(hPipe,szPipeQuery,szPipeQuery.GetLength(),
&cbBytes, &ol);
    if (!bResult && GetLastError() == ERROR_IO_PENDING)
        bResult = GetOverlappedResult(hPipe, &ol, &cbBytes, TRUE);
    while(true)
    {
        // here is the part to read pipe server responses
        // accomplished with ReadFile and GetOverlappedResult with parsing
        // abort the loop when the content is completely retrieved
        // or an error is occurred
    }
}

And here comes my problem. The server works for 30 requests or sometimes 200
requests. It's random. After that, the client starts to receive 231 error in
CreateFile. The actual client code handles this error and attempt 2 retries.
But from a certain point, the client will always receive 231 error when
connecting. At this point, from server trace messages, I saw that the server
has successfully processed previous requests, and waiting for new
connections. When the client receive 231, the server is actually at
WaitForMultipleObjects and hServerPipe is successfully created.

This might be because of some bug in the code I didn't post. But I found it
very difficult to debug. The server can successfully process several dozens
of requests. There is no error reported whatsoever. And all of the sudden,
the client just can't connect anymore. If I start a new instance of the
client. It'll also receive 231. Seems like the server is dead for some
reason.

How should I debug this problem? Could this be a thread synchronization
issue?

--
Best regards,
Bill Holt

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