如何判断某个IP的某个UDP端口是否开启？
Linux下用nmap就可以了：
如果显示open|filtered，表示可能是开启的或可能是过滤了
如果是： 端口/udp closed unknown 则表示端口未开启。
如果显示open，表示端口是开启的。
"nc -uvz ip port" isn't somehow accurate, you probably should use "nmap -sU -p port ip", if the result shows "open" then the udp port probably is open, if it shows "open|filtered" then probably it is closed or filtered.