求教 ：API 中重叠I/O的 使用 老是 读不出数据， 代码如 下

Question

var hcom : Thandle;
    Wrlap,Rdlap : Toverlapped;procedure TForm1.Button1Click(Sender: TObject);
VAR CC : TCommConfig;
begin
  hcom := createfile('com1',GENERIC_READ OR GENERIC_WRITE,0,nil,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL or FILE_FLAG_OVERLAPPED,0);
  if hcom = INVALID_HANDLE_VALUE then
  SHOWMESSAGE('打开串口失败')
  else
  begin
     GetCommState(hcom,CC.DCB);
     CC.dcb.BaudRate := CBR_9600;
     CC.dcb.StopBits := TWOSTOPBITS;
     CC.dcb.ByteSize := 8;
     CC.dcb.Parity:=NOPARITY;
     SetCommState(hcom,CC.dcb);
     SetupComm(hcom,2048,2048);
     //设置超时
     shape1.Brush.Color := clGreen;
  end;
end;procedure TForm1.Button2Click(Sender: TObject);
var number,lperror : longword;
    temp: String;
    coms : Tcomstat;
    dwNumberOfBytesWritten,ErrorFlag,dwEvtMask: Dword;
begin
  FillChar(Wrlap,SizeOf(Wrlap),0);
  Wrlap.hEvent   :=   CreateEvent(nil,True,FALSE,nil);
  temp := memo1.Text ;//这里我输入 的是发短信的 AT命令 
  WriteFile(hcom,pchar(temp)^, length(temp),dwNumberOfBytesWritten,@Wrlap)；
  ErrorFlag   := GetLastError;
    if   ErrorFlag=ERROR_IO_PENDING   then
        begin
          WaitForSingleObject(Wrlap.hEvent,1000);
        end
        else
        begin
          MessageBox(0,'WriteFile   Error!','Notice',MB_OK);
          Exit;
        end;end;procedure TForm1.Button3Click(Sender: TObject);var temp : String;
    lperror,dwNumberOfBytesRead : Longword;
    coms : Tcomstat;
    tmp : array [0..2047] of char;
begin
  ClearCommerror(hcom,lperror,@coms);
  FillChar(Rdlap,SizeOf(Rdlap),0);
  Rdlap.hEvent   :=   CreateEvent(nil,True,false,@Rdlap);
  lperror:=Getlasterror;
  IF NOT Readfile(hcom,tmp,coms.cbInQue,number,@Rdlap) Then
  begin
    if lperror = ERROR_IO_PENDING then
    begin;
    WaitForSingleObject(Rdlap.hEvent,1000);
    Getoverlappedresult(hcom,Rdlap.hEvent,dwNumberOfBytesRead,false);
    temp := copy(tmp,1,coms.cbInQue);
    end;
    memo2.Text := temp;
  end
  else
  memo2.Text := temp;
  purgeComm(hcom,PURGE_TXCLEAR or PURGE_RXCLEAR);
end;

Answer 1

unit comdemou; 
interface 
uses 
Windows, Messages, SysUtils, Classes, 
Graphics, Controls, Forms, Dialogs; const 
Wm_commNotify=Wm_User+12; 
type 
TForm1 = class(TForm) 
procedure FormCreate(Sender: TObject); 
private 
Procedure comminitialize; 
Procedure MsgcommProcess(Var 
Message:Tmessage); Message Wm_commnotify; 
{ Private declarations } 
public 
{ Public declarations } 
end; //线程声明 
TComm=Class(TThread) 
protected 
procedure Execute;override; 
end; var 
Form1: TForm1; 
hcom,Post_Event:Thandle; 
lpol:Poverlapped; 
implementation {$R *.DFM} Procedure TComm.Execute; //线程执行过程 
var 
dwEvtMask:Dword; 
Wait:Boolean; 
Begin 
fillchar(lpol,sizeof(toverlapped),0); 
While True do Begin 
dwEvtMask:=0; 
Wait:=WaitCommEvent(hcom,dwevtmask,lpol); 
//等待串行口事件； 
if Wait Then Begin 
waitforsingleobject(post_event,infinite); 
//等待同步事件置位； 
resetevent(post_event); //同步事件复位； 
PostMessage(Form1.Handle, 
WM_COMMNOTIFY,0,0);//发送消息； 
end; 
end; 
end; procedure Tform1.comminitialize; 
//串行口初始化 
var 
lpdcb:Tdcb; 
Begin 
hcom:=createfile('com2',generic_read or 
generic_write,0,nil,open_existing, 
file_attribute_normal or 
file_flag_overlapped,0);//打开串行口 
if hcom=invalid_handle_value then 
else 
setupcomm(hcom,4096,4096); 
//设置输入，输出缓冲区皆为4096字节 
getcommstate(hcom,lpdcb); 
//获取串行口当前默认设置 
lpdcb.baudrate:=2400; 
lpdcb.StopBits:=1; 
lpdcb.ByteSize:=8; 
lpdcb.Parity:=EvenParity; //偶校验 
Setcommstate(hcom,lpdcb); 
setcommMask(hcom,ev_rxchar); 
//指定串行口事件为接收到字符； 
end; Procedure TForm1.Msgcomm 
Process(Var Message:Tmessage); 
var 
Clear:Boolean; 
Coms:Tcomstat; 
cbNum,ReadNumber,lpErrors:Integer; 
Read_Buffer:array[1..100]of char; 
Begin 
Clear:=Clearcommerror(hcom,lpErrors,@Coms); 
if Clear Then Begin 
cbNum:=Coms.cbInQue; 
ReadFile(hCom,Read_Buffer, 
cbNum,ReadNumber,lpol); 
//处理接收数据 
SetEvent(Post_Event); 
//同步事件置位 
end; 
end; procedure TForm1.FormCreate(Sender: TObject); 
begin 
comminitialize; 
post_event:=CreateEvent 
(nil,true,true,nil); //创建同步事件； 
Tcomm.Create(False); 
//创建串行口监视线程； 
end; end. 

Answer 2

楼上的谢谢你的回复，
我连重叠I/O方式都没读到数据，监听的话也要用到 重叠I/O 噶