WriteFile(）和ReadFile(）异步不写入或读取

我正在尝试使用writefile和readfile函数通过串行端口连接发送和接收字符串。我必须异步地这样做，因为要读取的字节数总是不同的，而readfile只会挂起或阻塞，直到它得到正确的字节数。现在我正尝试异步执行此操作，我的writefile函数不会发送任何数据，而我的readfile函数似乎被跳过了，因为下一行开始执行它的操作，而没有读取任何字符。不确定是重叠结构有问题还是超时。但我此刻陷入了困境。

超时

void Serial::OpenPortRead()
{
HANDLE sSerial =  CreateFile(L"COM3",GENERIC_READ|GENERIC_WRITE,0,0,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,0);
//Timeout Settings
COMMTIMEOUTS    CommTimeouts;   
GetCommTimeouts(sSerial, &CommTimeouts);
CommTimeouts.ReadIntervalTimeout            = 5000; 
    CommTimeouts.ReadTotalTimeoutMultiplier     = 2; 
    CommTimeouts.ReadTotalTimeoutConstant       = 10; 
    CommTimeouts.WriteTotalTimeoutMultiplier    = 50; 
    CommTimeouts.WriteTotalTimeoutConstant      = 500; 
//Port Settings
DCB dcbSerialParams = {0};
dcbSerialParams.DCBlength=sizeof(dcbSerialParams);
dcbSerialParams.BaudRate=CBR_19200;
dcbSerialParams.ByteSize=8;
dcbSerialParams.StopBits=ONESTOPBIT;
dcbSerialParams.Parity=NOPARITY;
SetCommState(sSerial,&dcbSerialParams);//Apply Settings to Handle


}

写入文件功能

void Serial::WritePort(CString buffer)
{

DWORD bytes;//pointer to hold number of bytes written
USES_CONVERSION;
CW2A buf((LPCWSTR)buffer);//Convert unicode to ascii

OpenPortRead();
OVERLAPPED overlapped_structure;
memset(&overlapped_structure, 0, sizeof(overlapped_structure));
overlapped_structure.Offset = 0;
overlapped_structure.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
WriteFile(sSerial, buf,strlen(buf),&bytes,&overlapped_structure);//Send string

}

读取文件功能

int Serial::ReadPort(CString buf){
OpenPortRead();// Open Serial Communication for reading
const int buffer_size = 10;
 char buffer[10];//buffer to hold recieved string
memset (buffer, 0, buffer_size * sizeof (char));
int n, num,iTemp,i=0;
OVERLAPPED overlapped_structure;
memset(&overlapped_structure, 0, sizeof(overlapped_structure));
overlapped_structure.Offset = 0;
overlapped_structure.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
DWORD bytesRead;//pointer to number bytes read

ReadFile(sSerial,&buffer,buffer_size,&bytesRead,&overlapped_structure);// begin read

//Used this function because return would be filled with extra raw data characters
buffer[n] = StringLength(buffer, &n);//find length of string returned
num = n;