nc可以用来扫描端口，但是各个系统之间版本差别较大
centos7：
nc 不支持-r，i.e. 无法扫描端口范围。如果只测试一个端口可以用nc
[root@baidu ~]# nc -4vzw 1 www.baidu.com 81
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connection to 39.156.66.18 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection timed out.
[root@baidu ~]# nc -4vzw 1 www.baidu.com 80
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 39.156.66.18:80.
Ncat: 0 bytes sent, 0 bytes received in 0.03 seconds.
范围扫描可以用nmap
yum install nmap -y
[root@baidu ~]# nmap -sS -p 79-81 www.baidu.com
Starting Nmap 6.40 ( http://nmap.org ) at
Nmap scan report for www.baidu.com (39.156.66.14)
Host is up (0.0073s latency).
Other addresses for www.baidu.com (not scanned): 39.156.66.18
PORT STATE SERVICE
79/tcp filtered finger
80/tcp open http
81/tcp filtered hosts2-ns
Nmap done: 1 IP address (1 host up) scanned in 1.32 seconds
mac:
nc 支持-r，但是超时不用-w，这个nc忘了是不是系统自带的了，版本号都没查到
root@baidu ~ % nc -rvz -i 1 -G 1 39.156.66.18 79-81
Connection to 39.156.66.18 port 80 [tcp/http] succeeded!
nc: connectx to 39.156.66.18 port 81 (tcp) failed: Operation timed out
nc: connectx to 39.156.66.18 port 79 (tcp) failed: Operation timed out
百度承受了很多测试的责任，能力越大责任越大啊，哈哈蛤
其他的系统暂时未尝试，大家如果有好的方法欢迎留言