在RS232中有4个脚位可用来回应讯号给电脑分別为CTS,DSR,RING,RLSD当未接上设备时,脚位的电太皆为低电压,讯号传回OFF,很多设备都利用此四个脚位与电脑沟通,所以检查脚位电压就知道改COM上是否有设备存在 MS_CTS_ON,MS_DSR_ON,MS_RING_ON,MS_RLSD_ON PRocedure TForm1.Button1Click(Sender: TObject); var cc:TCommConfig; hComm:THandle; Com:String; lS:dWord; begin Com:='COM2'; hComm:=CreateFile(Pchar(Com),Generic_read or Generic_write,0,nil,open_existing,0,0); if GetCommModemStatus(hcomm,lS) then begin if(ls and MS_CTS_ON)=MS_CTS_ON then begin Button1.Caption:='CTSON' end; end; closeHandle(hcomm); end; (作者 anykey) end. 2.检查Handle所得到的值 procedure TForm1.Button1Click(Sender: TObject); var cc:TCommConfig; hComm:THandle; Com:String; lS:dword; begin Com:='COM2'; hComm:=CreateFile(Pchar(Com),Generic_read or Generic_write,0,nil,open_existing,0,0); if(hComm=invalid_Handle_value) then begin showmessage('通讯口错误); end; closeHandle(hcomm); end;(作者 anykey)
