获取网页源码socket error #10061,该怎么处理

procedure TForm1.Button1Click(Sender: TObject);
var
  HTML: String;
  IdHTTP1: TIdHTTP;
begin
  HTML := '';
  try
    IdHTTP1:= TIdHTTP.Create(nil);
    IDHttp1.HandleRedirects := true;
    IdHTTP1.request.contenttype:='application/x-www-form-urlencoded';

    try
      //HTML := IdHTTP1.Get('http://xxxxx.com/b.html');    //这个可以正常获取
      [color=#FF0000]HTML := IdHTTP1.Get('C:\b.html');[/color]    //这个报错
      HTML := UTF8Decode(HTML);
    except
    end;
  finally
    IdHTTP1.Free;
  end;
  Application.MessageBox(pchar(HTML),'提示',0)
end;