function TCustomComPort.WaitForAsync(var AsyncPtr: PAsync): Integer;
var
  BytesTrans, Signaled: DWORD;
  Success: Boolean;
begin
  if AsyncPtr = nil then
    //raise EComPort.CreateNoWinCode
    CallException(CError_InvalidAsync);

  //Signaled := WaitForSingleObject(AsyncPtr^.Overlapped.hEvent, INFINITE);
  Signaled := WaitForSingleObject(AsyncPtr^.Overlapped.hEvent, 100);
  Success := (Signaled = WAIT_OBJECT_0) and
      (GetOverlappedResult(FHandle, AsyncPtr^.Overlapped, BytesTrans, False));

  if not Success then
    //raise EComPort.Create
    CallException(ErrorCode(AsyncPtr), GetLastError);

  if (AsyncPtr^.Kind = okRead) and (InputCount = 0) then
    SendSignalToLink(leRx, False)
  else
    if AsyncPtr^.Data <> nil then
      TxNotifyLink(AsyncPtr^.Data^, AsyncPtr^.Size);

  Result := BytesTrans;
end;

procedure TCustomComPort.AbortAllAsync;
begin
  try
  if not PurgeComm(FHandle, PURGE_TXABORT or PURGE_RXABORT) then
    raise EComPort.Create (CError_PurgeFailed, GetLastError);
    //CallException(CError_PurgeFailed, GetLastError);
  except

  end;
end;

procedure TCustomComPort.Close;
begin
   // if already closed, do nothing
      if FConnected and not(csDesigning in ComponentState) then
      begin
        CallBeforeClose;
        // abort all pending operations
try
        AbortAllAsync;
finally
        // stop monitoring for events
        if FThreadCreated then
        begin
          FEventThread.Free;
          FThreadCreated := False;
          if FSyncMethod = smWindowSync then
{$IFDEF DELPHI_6_OR_HIGHER}
{$WARN SYMBOL_DEPRECATED OFF}
{$ENDIF}
            DeallocateHWnd(FWindow);
{$IFDEF DELPHI_6_OR_HIGHER}
{$WARN SYMBOL_DEPRECATED ON}
{$ENDIF}
        end;
        // close port
        DestroyHandle;
        FConnected := False;
        // port is closed, do any additional finalization
        CallAfterClose;
      end;
end;
end;

function TCustomComPort.WriteStr(Str: string): Integer;
var
  AsyncPtr: PAsync;
begin
  InitAsync(AsyncPtr);
  try
    WriteStrAsync(Str, AsyncPtr);
    Result := WaitForAsync(AsyncPtr);
  finally
    DoneAsync(AsyncPtr);
  end;
end;

function TCustomComPort.WriteStrAsync(var Str: string; var AsyncPtr: PAsync): Integer;
var sa : Ansistring; var i:integer;
begin

  if Length(Str) > 0 then
  begin
    setlength(sa,length(str));
    {$IFDEF Unicode}
    if length(sa)>0 then
    begin
      for i := 1 to length(str) do sa[i] := ansichar(byte(str[i]));
      move(sa[1],str[1],length(sa));
    end;
    {$ENDIF}
      Result := WriteAsync(Str[1], Length(Str), AsyncPtr)

  end
  else
    Result := 0;

end;