Being able to find open ports are really important. The command to find out used to be:
netstat
But now it has changed to simply ss. In this case, I have add tunpl, This is
t - tcp
u - udp
n - network
l - long output
p - process ip
glasco@klingon:~/Downloads$ ss -tunpl
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
udp UNCONN 0 0 0.0.0.0:35784 0.0.0.0:*
udp UNCONN 0 0 192.168.1.154:3702 0.0.0.0:* users:(("wsdd",pid=5934,fd=12))
udp UNCONN 0 0 239.255.255.250:3702 0.0.0.0:* users:(("wsdd",pid=5934,fd=10))
udp UNCONN 0 0 224.0.0.251:5353 0.0.0.0:* users:(("chrome",pid=9741,fd=351))
udp UNCONN 0 0 0.0.0.0:5353 0.0.0.0:*
udp UNCONN 0 0 0.0.0.0:5355 0.0.0.0:*
udp UNCONN 0 0 0.0.0.0:55697 0.0.0.0:* users:(("firefox",pid=3083,fd=144))
udp UNCONN 0 0 0.0.0.0:60851 0.0.0.0:* users:(("firefox",pid=3083,fd=149))
udp UNCONN 0 0 127.0.0.54:53 0.0.0.0:*
udp UNCONN 0 0 127.0.0.53%lo:53 0.0.0.0:*
udp UNCONN 0 0 127.0.0.1:323 0.0.0.0:*
udp UNCONN 0 0 0.0.0.0:33942 0.0.0.0:* users:(("wsdd",pid=5934,fd=11))
udp UNCONN 0 0 [fe80::cc98:92bc:fd5c:648c]%wlp2s0:3702 [::]:* users:(("wsdd",pid=5934,fd=9))
udp UNCONN 0 0 [ff02::c]%wlp2s0:3702 [::]:* users:(("wsdd",pid=5934,fd=7))
udp UNCONN 0 0 [::]:5353 [::]:*
udp UNCONN 0 0 [::]:5355 [::]:*
udp UNCONN 0 0 [::]:47670 [::]:*
udp UNCONN 0 0 *:59161 *:* users:(("wsdd",pid=5934,fd=8))
udp UNCONN 0 0 [::1]:323 [::]:*
tcp LISTEN 0 4096 127.0.0.1:631 0.0.0.0:*
tcp LISTEN 0 10 0.0.0.0:27500 0.0.0.0:*
tcp LISTEN 0 4096 127.0.0.53%lo:53 0.0.0.0:*
tcp LISTEN 0 4096 127.0.0.54:53 0.0.0.0:*
tcp LISTEN 0 4096 0.0.0.0:5355 0.0.0.0:*
tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:*
tcp LISTEN 0 4096 [::1]:631 [::]:*
tcp LISTEN 0 4096 [::]:5355 [::]:*
tcp LISTEN 0 128 [::]:22 [::]:*
glasco@klingon:~/Downloads$
The ports with the state LISTEN are tcp ports like secure shell on tcp port 22.
To show open ports on older systems it used to be 'netstat' rather than 'ss' followed by the exact same parameters. (I mention this as there are older government systems still up and running.