string(311) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E7%AE%80%E8%BF%B0%E4%BA%92%E8%81%94%E7%BD%91%E6%8A%80%E6%9C%AF%E5%8F%91%E5%B1%95%E7%9A%84%E5%90%84%E4%B8%AA%E9%98%B6%E6%AE%B5%E5%8F%8A%E5%85%B6%E7%89%B9%E5%BE%81 => Received HTTP code 403 from proxy after CONNECT"
简述互联网技术发展的各个阶段及其特征
