如何对并口进行读写

[moneycao]

我最近在编写并口读写的程序，但是一直不成功，代码如下：
OVERLAPPED overlapped; //OVERLAPPED structure
OVERLAPPED overlappedread;
OVERLAPPED overlappedwrite;
overlapped.Internal=0;
overlapped.InternalHigh=0;
overlapped.Offset=0;
overlapped.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);

HANDLE FHandle = CreateFile( "\\\\.\\LPT1",
GENERIC_READ | GENERIC_WRITE,
0, // Not shared
NULL, // No security attributes
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,// asynchronism communication
0
);

if(GetLastError()==0)
{
overlappedwrite.Internal=0;
overlappedwrite.InternalHigh=0;
overlappedwrite.Offset=0;
overlappedwrite.OffsetHigh=0;
overlappedwrite.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);
//这个很重要，不信你可以注释掉，看看结果会怎样。
LPCVOID csp="dgfdfgfd";
LPDWORD nSent;
WriteFile( FHandle,&csp,8,nSent, &overlappedwrite);

}
else
ShowMessage("并口初始化失败！");
CloseHandle(FHandle);
但执行到WriteFile( FHandle,&csp,8,nSent, &overlappedwrite);时出错
还有我如何能知道并口有数据传过来。