string(241) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E5%9B%BD%E5%86%85%E6%AF%94%E8%BE%83%E5%A5%BD%E7%9A%84dns%E5%9C%B0%E5%9D%80 => Failed to connect to 14.18.117.71 port 38133: Connection refused"
国内比较好的dns地址
