Try this before ReadFile :
BOOL WINAPI PeekNamedPipe(
__in HANDLE hNamedPipe,
__out_opt LPVOID lpBuffer,
__in DWORD nBufferSize,
__out_opt LPDWORD lpBytesRead,
__out_opt LPDWORD lpTotalBytesAvail,
__out_opt LPDWORD lpBytesLeftThisMessage
);
if(TotalBytesAvail > 0)
ReadFile(....);
-AV-