string(233) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=b2b%E6%A8%A1%E5%BC%8F%E6%98%AF%E4%BB%80%E4%B9%88%E6%A0%B7%E7%9A%84%E6%A8%A1%E5%BC%8F => Received HTTP code 403 from proxy after CONNECT"
b2b模式是什么样的模式
