未定义问题

   近来在学习网络间的通讯，遇到不解的问题，请各位解答一下，
type
    TForm1 = class(TForm)
    Timer1: TTimer;
    Label1: TLabel;
    Label2: TLabel;
    IdTCPClient1: TIdTCPClient;
    IdTCPVfw: TIdTCPClient;
    procedure CreateCaptureWindow;
    procedure FormShow(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
  private
    { Private declarations }
    procedure CompareFrame(lpVHdr: PVIDEOHDR);
    procedure StopCapture;
  public
    procedure SendStreamToClient(AThread: TIdTCPClient;Cmd,TempStr:String); 
    procedure ControlCommand(var RDStrList:TStringList);
    { Public declarations }
  end;TClientHandleThread = class(TThread)   //接收线程类  接收线程单元
                         private
                           CommandStr:String;
                           procedure HandleInput;
                         protected
                           procedure Execute; override;
                         Public
                           constructor Create;
                           destructor Destroy; override;
                        end;type里面明明定义了IdTCPVfw，但我在下面写的procedure TClientHandleThread.HandleInput;过程里却出现idTCPVfw未定义的错误，什么原因？