string(265) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E8%B4%A8%E9%87%8F%E6%8E%A7%E5%88%B6%E7%9B%B4%E6%96%B9%E5%9B%BE%E7%BB%98%E5%88%B6%E4%BE%8B%E9%A2%98 => Failed to connect to 61.171.74.35 port 38027: Connection refused"
质量控制直方图绘制例题
