API串口通信,打开,设置串口都正确,为什么数据发送不出?

Question

char * sendstring="hello world!";
    char readstring[100];
    unsigned long int len,fact_len,fact_send_len;
    DCB dcb;
    HANDLE hCom;
     COMMTIMEOUTS timeout;
     OVERLAPPED Write_OverLapped,Read_OverLapped;
     len=fact_len=fact_send_len=0;
  hCom=CreateFile("COM1",GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);
    if( hCom == INVALID_HANDLE_VALUE )
    {
        ShowMessage( "串口打开失败" );
    }
    else
    {
            GetCommState(hCom, &dcb ) ; //读串口原来的参数设置
            dcb.BaudRate=9600;
            dcb.ByteSize=8;
            dcb.Parity = NOPARITY;
            dcb.StopBits=ONESTOPBIT;
            if(SetCommState(hCom,&dcb))
                    ShowMessage("OK");            SetupComm(hCom,1024,1024);
            timeout.ReadIntervalTimeout=20;
            timeout.ReadTotalTimeoutMultiplier=1000;
            timeout.ReadTotalTimeoutConstant=1000;
            timeout.WriteTotalTimeoutMultiplier=1000;
            timeout.WriteTotalTimeoutConstant=1000;
           SetCommTimeouts(hCom,&timeout);
            PurgeComm( hCom, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR ); //清干净输入、输出缓冲区
            len=strlen(sendstring);       bool fWriteState=WriteFile(hCom,sendstring,len,&fact_len,&Write_OverLapped);
             if (!fWriteState) {
                                  while(!GetOverlappedResult(hCom,&Write_OverLapped,&fact_send_len,true))
                                                      continue;
                               }
              
               if(Write_OverLapped.hEvent!=NULL)
                        ShowMessage("发送完");
         
    }      CloseHandle(hCom);  
------------------------
fact_send_len始终为0. 
请问有什么错误?不要多线程.

Answer 1

你的write_overlapped 要初始化，并且要赋一个信号量给它，
MemorySet(&write_overlapped,sizeof(write_overlapped);
HANLE hEvent = CreateEvent(NULL, FALSE, FALSE,"");
write_overlapped.hEvent = hEvent;
就可以了，呵呵，我也正在做这个，也是这个问题.

Answer 2

bool CCommDlg::WriteCommBlock(LPVOID lpstr, DWORD dwBytesToWrite)
{
DWORD dwBytesWritten, dwBytesSent = 0;
OVERLAPPED os; memset(&os, 0, sizeof(os));
os.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if(!WriteFile(m_hComm, lpstr, dwBytesToWrite,
&dwBytesWritten, &os)) {
if(GetLastError() == ERROR_IO_PENDING) {
while(!GetOverlappedResult(m_hComm, &os, &dwBytesWritten, TRUE)) {
if(GetLastError() == ERROR_IO_INCOMPLETE) {
dwBytesSent += dwBytesWritten;
continue;
}
else {
ShowError();
break;
}
}
dwBytesSent += dwBytesWritten;
if(dwBytesSent != dwBytesToWrite) {
CloseHandle(os.hEvent);
return false;
}
} else { //不是ERROR_IO_PENDING，出错
ShowError();
CloseHandle(os.hEvent);
return false;
}
} CloseHandle(os.hEvent);
return true;
}

Answer 3

多谢二位!可以发送啦!可是却无法读出数据来!
if(Write_OverLapped.hEvent!=NULL)
               //发送完
               {
                 Read_OverLapped.hEvent=CreateEvent(NULL,true,NULL,NULL);
                 ReadFile(hCom,readstring,100,&fact_len,&Read_OverLapped);
                 while(!GetOverlappedResult(hCom,&Read_OverLapped,&fact_read_len,true))
                    continue;               }