以下为使用 nmap 工具扫描局域网内所有主机的打开的端口的例子。nmap 工具可以上 http://insecure.org/nmap 网站下载。
C:\Program Files\nmap-5.21>nmap -sT 110.75.164.1 | more
Starting Nmap 5.21 ( http://nmap.org ) at 2010-02-05 04:19 中国标准时间
Nmap scan report for 110.75.164.1
Host is up (0.00s latency).
Not shown: 999 filtered ports
PORT STATE SERVICE
21/tcp open ftp
Nmap done: 1 IP address (1 host up) scanned in 50.42 seconds