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我使用C++ Builder 6.0调用Win32 API实现的。
首先开一个线程。
void __fastcall TForm1::FormCreate(TObject *Sender)
{
           ReadComm =new TRead232(true);
        ReadComm->FreeOnTerminate = true;    
}
通过一个按钮实现打开/关闭串口
void __fastcall TForm1::Button1Click(TObject *Sender)
{
    if(Button1->Caption == "打开通讯端口")  //按钮名称是"打开通讯端口"？
    {
        char *ComNo;
        DCB dcb;
        String Temp;
        Temp = "COM"+IntToStr(rdCom->ItemIndex+1);
//        TRadioGroup *rdCom; 定义要选择的串口
        ComNo = Temp.c_str();
        hComm =CreateFile(ComNo,GENERIC_READ|GENERIC_WRITE,
                0,NULL,OPEN_EXISTING,0,0);
        if(hComm == INVALID_HANDLE_VALUE)
        {
                MessageBox(0,"打开串口失败!!","Set Error",MB_OK);
                return;
        }
        GetCommState(hComm,&dcb);
        dcb.BaudRate = CBR_9600;
        dcb.ByteSize = 8;
        dcb.Parity = NOPARITY;
        dcb.StopBits = ONESTOPBIT;
        if(!SetCommState(hComm,&dcb))
        {
                MessageBox(0,"打通讯端口设置错误!!","Set Error",MB_OK);
                CloseHandle(hComm);
                return;
        }
        Timer1->Enabled = True;
        Button1->Caption = "关闭串口";
        Shape1->Brush->Color = clRed;
        //启动接收线程

        ReadComm->Resume();
    }
    else
    {
        Button1->Caption = "打开通讯端口";
        CloseHandle(hComm);
        Shape1->Brush->Color = clBlack;
        Timer1->Enabled = False;
        ReadComm->Terminate();

    }
}
接收由线程TRead232完成
void __fastcall TRead232::Execute()
{
        SetName();
        //---- Place thread code here ----
        if(!Terminated) Synchronize(ReadData);
}
//---------------------------------------------------------------------------
void __fastcall TRead232::ReadData()
{
         Form1->Caption = "Updated in a thread";

        String Temp;
        char inbuff[1024];
        DWORD nBytesRead,dwEvent,dwError;
        COMSTAT cs;
        if(hComm == INVALID_HANDLE_VALUE)
        {
             MessageBox(0,"串口失败!!","Set Error",MB_OK);

                return;
        }
        ClearCommError(hComm,&dwError,&cs);
        Form1->Edit1->Text = cs.cbInQue;
        if(cs.cbInQue > sizeof(inbuff))
        {
                PurgeComm(hComm,PURGE_RXCLEAR);
                return;
        }
        ReadFile(hComm,inbuff,cs.cbInQue,&nBytesRead,NULL);
        inbuff[cs.cbInQue]='\0';
        Form1->Memo1->Text =Form1->Memo1->Text+inbuff;
}
发送是定时器TIMER1触发，定时发送的。
void __fastcall TForm1::Timer1Timer(TObject *Sender)
{
        char SendData[20];
        byte ch;
        int i;
        unsigned long lrc,BS;
        if (hComm==0) return;
        SendData[0] = 0x41;
        SendData[1] = 0x03;
        SendData[2] = 0x00;
        SendData[3] = 0x01;
        SendData[4] = 0x00;
        SendData[5] = 0x04;
        SendData[6] = 0x1b;
        SendData[7] = 0x09;
        SendData[8] = '\0';
//        BS = 8;           // StrLen(SendData);
        for(i=0;i<=7;i++)
        {
                ch = SendData[i];
                WriteFile(hComm,&ch,1,&lrc,NULL);
        }
}