string(232) "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%8C%87%E7%9A%84%E6%98%AF%E4%BB%80%E4%B9%88 => Failed to connect to 61.171.74.35 port 38027: Connection refused"
b2b模式指的是什么
