设置串口读写超时

//注：读写方式为同步，另，此方法对虚拟串口无效。
  HANDLE hCom1=CreateFile(_T("COM1"),GENERIC_WRITE|GENERIC_READ,0,NULL,OPEN_EXISTING,
                            0,NULL);
   if(hCom1==INVALID_HANDLE_VALUE)
   MessageBox(0,0,0,0);
   DCB dcb;
   if(GetCommState(hCom1,&dcb))
   {
       dcb.BaudRate=CBR_115200;
       dcb.ByteSize=8;
       dcb.Parity=NOPARITY;
       dcb.StopBits=2;
       int err;
       if(!SetCommState(hCom1,&dcb))
       {
           err=GetLastError();
	   CloseHandle(hCom1);
	   MessageBox(0,0,0,0);
       }
       COMMTIMEOUTS ct;
       if(GetCommTimeouts(hCom1,&ct))
       {
           ct.ReadTotalTimeoutConstant=1000;
           ct.ReadIntervalTimeout=1000;
           ct.ReadTotalTimeoutMultiplier=1000;
           if(!SetCommTimeouts(hCom1,&ct))
           {
	    CloseHandle(hCom1);
            err=GetLastError();
            MessageBox(0,0,0,0);
           }
       }
       SetupComm(hCom1,1024,1024);
       PurgeComm(hCom1,   PURGE_TXABORT   |   PURGE_RXABORT   |   PURGE_TXCLEAR   |   PURGE_RXCLEAR);
       DWORD dwRead;
       CHAR pRead[1024]="";
       DWORD dwtime=GetTickCount();
       err=ReadFile(hCom1,&pRead,1024,&dwRead,NULL);
       DWORD dwtimeout=GetTickCount()-dwtime;
       	      
       CloseHandle(hCom1);
   }