string(234) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E7%AE%80%E8%BF%B0b2b%E6%A8%A1%E5%BC%8F%E7%9A%84%E4%BC%98%E5%8A%BF => Failed to connect to 101.89.159.206 port 38187: Connection refused"
简述b2b模式的优势
