TIdUDPServer的问题，难道是因为D版的delphi7的原因吗？

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, IdBaseComponent, IdComponent, IdUDPBase, IdUDPServer, StdCtrls;type
  TForm1 = class(TForm)
    Button1: TButton;
    IdUDPServer1: TIdUDPServer;
    procedure Button1Click(Sender: TObject);
    procedure IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
      ABinding: TIdSocketHandle);  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.Button1Click(Sender: TObject);
begin
IdUDPServer1.Send('127.0.0.1',2000,'lskjdf');
end;procedure TForm1.IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
  ABinding: TIdSocketHandle);
begin
showmessage('received');
end;end.错误：  [Error] Unit1.pas(15): Undeclared identifier: 'TIdSocketHandle'
  [Fatal Error] Project1.dpr(5): Could not compile used unit 'Unit1.pas'请问是怎么回事？难道是因为盗版的delphi7的原因吗？