string(252) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=b2b%E7%9A%84%E4%B8%BB%E8%A6%81%E6%A8%A1%E5%BC%8F%E6%9C%89%E5%93%AA%E5%87%A0%E7%A7%8D => Failed to connect to 101.89.143.195 port 38205: Connection refused"
b2b的主要模式有哪几种
