string(320) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E8%AF%B7%E7%AE%80%E8%BF%B0%E4%BA%92%E8%81%94%E7%BD%91%E5%8F%91%E5%B1%95%E7%9A%84%E5%8E%86%E5%8F%B2%E9%98%B6%E6%AE%B5%E5%8F%8A%E5%90%84%E9%98%B6%E6%AE%B5%E7%89%B9%E7%82%B9 => Received HTTP code 403 from proxy after CONNECT"
请简述互联网发展的历史阶段及各阶段特点
