sp;     CloseHandle(Post_Event);

              CloseHandle(hNewCommFile);

              Exit;

            end

          else

            begin           

              WaitForSingleObject(hNewCommFile,INFINITE); // 等待操作完成

              GetOverlappedResult(hNewCommFile,Read_os,

                                  dwNumberOfBytesRead,False);

            end;

        end;

      if dwNumberOfBytesRead>0 then

        begin

          Read_Os.Offset :=Read_Os.Offset+dwNumberOfBytesRead;

          ReceiveData := Read_Os.Offset;

          // 处理接收的数据

          AddToMemo(InputBuffer,dwNumberOfBytesRead);

        end;

end;

  // 允许发送下一个WM_COMMNOTIFY消息

  SetEvent(Post_Event);

end;

  

procedure TForm1.Button1Click(Sender: TObject); // 打开文件用于发送

begin

  if OpenDialog1.Execute then

    begin

      Button3.Enabled :=False;

      Button4.Enabled :=False;

      RichEdit1.Lines.LoadFromFile(OpenDialog1.FileName);

      Form1.Caption := IntToStr(RichEdit1.GetTextLen);

    end;

    Button1.Enabled :=False;

end;

  

procedure TForm1.Button2Click(Sender: TObject); // 发送数据

var

  dcb : TDCB;

  Error :Boolean;

  dwNumberOfBytesWritten,dwNumberOfBytesToWrite,

  ErrorFlag,dwWhereToStartWriting : DWORD;

  pDataToWrite : PChar;

  write_os: Toverlapped;

begin

  Form1.Caption :='''';

  // 打开通讯端口COM2

  hNewCommFile:=CreateFile( ''COM2'',GENERIC_WRITE,0,

                           nil, OPEN_EXISTING,FILE_FLAG_OVERLAPPED,0 );

  if hNewCommFile = I