nmap 扫描服务器开放了哪些端口

apt-get install nmap

nmap -sS -p 0-1000 xxx.xxx.xxx.xxx

输出：

Starting Nmap 6.40 ( http://nmap.org ) at 2016-11-08 16:41 CST Nmap
scan report for xxx.xxx.xxx.xxx Host is up (0.0000090s latency). Not
shown: 998 closed ports PORT STATE SERVICE 22/tcp open ssh 80/tcp
open http 81/tcp open hosts2-ns

Nmap done: 1 IP address (1 host up) scanned in 2.43 seconds

可以看到开放了22 80 81端口

Nmap基本使用教程
https://www.cnblogs.com/Acewipe/p/7589022.html
Nmap 下载
https://nmap.org/download.html