string(238) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E4%BA%8C%E5%BB%BA%E5%AE%98%E6%96%B9%E6%8C%87%E5%AE%9A%E6%95%99%E6%9D%90 => Failed to connect to 14.18.117.71 port 38133: Connection refused"
二建官方指定教材
