方法一：使用netstat命令（需要net-tools包）
[root@sre01 ~]# netstat -tan
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:234 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
tcp 0 0 192.168.236.100:22 192.168.236.1:59783 ESTABLISHED
tcp 0 0 192.168.236.100:22 192.168.236.1:64133 ESTABLISHED
tcp 0 0 192.168.236.100:22 192.168.236.1:65122 ESTABLISHED
tcp 0 0 192.168.236.100:22 192.168.236.1:63730 ESTABLISHED
tcp6 0 0 ::1:25 :::* LISTEN
tcp6 0 0 :::234 :::* LISTEN
tcp6 0 0 :::22 :::* LISTEN
[root@sre01 ~]# netstat -lntp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1314/master
tcp 0 0 0.0.0.0:234 0.0.0.0:* LISTEN 6184/nc
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1164/sshd
tcp6 0 0 ::1:25 :::* LISTEN 1314/master
tcp6 0 0 :::234 :::* LISTEN 6184/nc
tcp6 0 0 :::22 :::* LISTEN 1164/sshd
[root@sre01 ~]# netstat -lnup
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
udp 0 0 0.0.0.0:68 0.0.0.0:* 3340/dhclient
[root@sre01 ~]# netstat -lnap
Active Internet connections (servers and established)方法二：使用ss命令
[root@sre01 ~]# ss -lnt
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 100 127.0.0.1:25 *:*
LISTEN 0 10 *:234 *:*
LISTEN 0 128 *:22 *:*
LISTEN 0 100 [::1]:25 [::]:*
LISTEN 0 10 [::]:234 [::]:*
LISTEN 0 128 [::]:22 [::]:*
[root@sre01 ~]# ss -lnu
State Recv-Q Send-Q Local Address:Port Peer Address:Port
UNCONN 0 0 *:68 *:* 
