yum install net-tools
yum install nc.x86_64
apt install netcat
netstat -tunlp
cat /proc/sys/net/ipv6/bindv6only
netstat -i
netstat -tunlp | grep ssh
netstat -anp | grep ":80"
netstat -s
netstat -st
netstat -su
nc -6 -l 80
nc -4 -l 80
nc -l 80
nc localhost 80
nc -l 80 > /tmp/nc.txt
nc localhost 80 < /tmp/file.txt
nc -zv netnr.com 80
nc -zvn 114.114.114.114 53
nc -uvz 127.0.0.1 323
yum install epel-release
yum install iftop htop smem
iftop -i eth0 -n -P
smem -tkP postgres
ps aux | grep mysql
https://www.cnblogs.com/huangjiabobk/p/18075142