string(258) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E5%8F%98%E5%8A%A8%E6%88%90%E6%9C%AC%E7%9A%84%E8%AE%A1%E7%AE%97%E6%96%B9%E6%B3%95%E6%98%AF => Failed to connect to 101.89.143.195 port 38205: Connection refused"
变动成本的计算方法是
