2023
https://linuxhandbook.com/ufw-logs/
2022
https://linuxhandbook.com/close-open-ports/
2021
https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-with-ufw-on-ubuntu-18-04


pacman -Ss gufw

sudo ufw
    status [numbered|verbose]
    disable
    reload
    reset

    allow <RULE>
        <port>[/<proto>]
    deny <RULE>

    app
        list
        default <arg>
        info <profile>
        update <profile>

    logging
        on
        <logging_level>
            off|low|medium|high|full
        less /var/log/ufw.log

cfg-file:
    /etc/default/ufw

misc
TCP port check:
nc -w 10 -vz a.b.c.d 443

HTTPS check:
timeout 10 curl -I https://a.b.c.d


80                         ALLOW       Anywhere                  
8443                       ALLOW       Anywhere                  
9000                       ALLOW       Anywhere                  
80 (v6)                    ALLOW       Anywhere (v6)             
8443 (v6)                  ALLOW       Anywhere (v6)             
9000 (v6)                  ALLOW       Anywhere (v6)