使用nc命令来探测tcp/udp端口
usage: nc [-46DdhklnrStUuvzC] [-i interval] [-p source_port] [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_version]
usage: nc [-46DdhklnrStUuvzC] [-i interval] [-p source_port] [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_version]