string(265) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E6%B5%81%E9%87%8F%E8%AE%A1%E4%BC%A0%E6%84%9F%E5%99%A8%E7%9A%84%E5%B7%A5%E4%BD%9C%E5%8E%9F%E7%90%86 => Failed to connect to 14.18.117.71 port 38041: Connection refused"
流量计传感器的工作原理
