Порт Ввода-вывода, ошибка записи в файл?

m_hFile = CreateFile((LPCTSTR) pstrFilePath->GetString(), GENERIC_WRITE, NULL, NULL, 
                  CREATE_ALWAYS, FILE_FLAG_SEQUENTIAL_SCAN | FILE_FLAG_OVERLAPPED, NULL);
return (m_hFile != INVALID_HANDLE_VALUE);

fOk = (CreateIoCompletionPort(m_hFile, m_hIOCP, CompKey, dwNumberOfThread) == m_hIOCP);

BOOL fOk = ::WriteFile(m_hFile, (LPCVOID) m_pWbufSend->buf, dwBytesWrite, 
                        NULL, m_pOverlapSend);
if ( fOk == FALSE ) {
    if ( WSA_IO_PENDING != WSAGetLastError() )
        ThrowWSASocketException( WSAGetLastError() );
}
return ( FALSE );

pListenServer->GetStatus((PULONG_PTR)&pAcceptClient, &dwBytesTransfer/*, dwMilliseconds*/);

BOOL GetStatus(PULONG_PTR pCompKey, PDWORD pdwNumBytes, DWORD dwMilliseconds = INFINITE)    {
    LPWSAOVERLAPPED pOverlapped = NULL;
    DWORD dwResult = m_pIocp->GetStatus(pCompKey, pdwNumBytes, &pOverlapped, dwMilliseconds);
    return dwResult;
}

fOk = (CreateIoCompletionPort(m_hFile, m_hIOCP, CompKey, dwNumberOfThread) == m_hIOCP);

void add( const HANDLE new_hdl, ULONG_PTR key ) {
    error_checker chker( WAPIE("IOCP::add") );
    m_handle = chker = CreateIoCompletionPort(new_hdl, m_handle.hdl(), key, 0);
}
 
// success = true
// timeout = false
// error = throw
bool wait( ULONG_PTR & key, DWORD &transferred, DWORD miliseconds) const {
    error_checker chker( WAPIE("IOCP::wait"), WAIT_TIMEOUT );
    LPOVERLAPPED  povl = NULL;
    BOOL res = chker = GetQueuedCompletionStatus(m_handle.hdl(), 
                &transferred, 
                &key, 
                &povl, miliseconds);
    return res ? true : false;
}

/////////////////////////////////////////////////////////////////////////////
// CAcceptClient
class CAcceptClient
{
....
private:
    ...
    IO_OPERATION_DATA* m_pioData;   //  Стуктура OVERLAPPED и буфер (см ниже)
    HANDLE m_hFile;
    ...
public:
    DWORD OpenFile...
    void CloseFile();

PCAcceptClient pAcceptClient=(PCAcceptClient) VirtualAlloc(NULL, sizeof(CAcceptClient),...
...
// Ассоциируем  сокет клиента с портом завершения
m_pIocp->AssociateSocket( pAcceptClient->GetSocket(), (ULONG_PTR) pAcceptClient );

BOOL AssociateDevice(HANDLE hDevice, ULONG_PTR CompKey) {
  BOOL fOk=(CreateIoCompletionPort(hDevice, m_hIOCP, CompKey, dwNumberOfThread)==m_hIOCP);
  ASSERT(fOk);
  return(fOk);
}
 
BOOL AssociateSocket(SOCKET hSocket, ULONG_PTR CompKey) {
    return(AssociateDevice((HANDLE) hSocket, CompKey));
}

// Ожидаем завершения операции ввода/вывода  на любом сокете, связанным с данным портом
dwBytesTransfer= 0;
if ( dwResult=pListenServer->GetStatus( (PULONG_PTR)&pAcceptClient, &dwBytesTransfer ) ){
    if ( dwResult == (DWORD)-1 )
        ThrowWSASocketException;//  socket закрыт ПРОВЕРЕНО
    else
        dwBytesTransfer = 0;
    }
 
    ASSERT_POINTER(pAcceptClient, CAcceptClient);

class IO_OPERATION_DATA /*: public OVERLAPPED*/
{
...
private:
    u_long          m_ulBuffBytes;
    LPWSAOVERLAPPED m_pOver;
    LPWSABUF        m_pwbuf;

wapi_file_handle f(L"C:\\tmp.txt");
    f.create();
    OVERLAPPED ovl;
    DWORD w;
    BOOL res = WriteFile(f.hdl(), "111", 3, &w, &ovl);// тут получим 6, хотя хендл живой

wapi_file_handle f(L"C:\\tmp.txt");
    f.create();
    OVERLAPPED ovl = {0}; // !!
    DWORD w;
    BOOL res = WriteFile(f.hdl(), "111", 3, &w, &ovl); // тут все ok, получаем или err=0 или err=997