老是出错！

d7下的用UDP收发的一个小程序。但是一运行就出错老是说我没有声明undeclared identifier'tidsockethandel'
到底什么怎么了哦？。第一次接触indy；谢谢！type
  TForm1 = class(TForm)
    IdUDPClient1: TIdUDPClient;
    IdUDPServer1: TIdUDPServer;
    CheckBox1: TCheckBox;
    Edit1: TEdit;
    Memo1: TMemo;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
      ABinding: TIdSocketHandle);///错就在这里，undeclared identifier'tidsockethandel'
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.Button1Click(Sender: TObject);
  var
    bf:TMemoryStream;
begin
  IdUDPClient1.Host:='127.0.0.1';
  IdUDPClient1.Port:=9090;
  IdUDPClient1.Active:=True;
  if CheckBox1.Checked  then
    begin
      IdUDPClient1.Send(Edit1.Text);
      bf.Clear;
      bf.Position:=0;
      bf.LoadFromFile('test.bmp');
      IdUDPClient1.SendBuffer(bf,bf.Size);
    end;end;procedure TForm1.FormCreate(Sender: TObject);
begin
  IdUDPServer1.DefaultPort:=9090;
  IdUDPServer1.Active:=True;
end;procedure TForm1.IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
  ABinding: TIdSocketHandle);
    var
      tempstream:TStringStream;
begin
  tempstream:=TStringStream.Create('');
  tempstream.CopyFrom(AData,AData.Size);
  Memo1.Lines.Add(tempstream.DataString);
  tempstream.Free;end;end.