ufw (Uncomplicated FireWall) commands are complicated, but there is a cheat sheet here

From Ubuntu help:

The default firewall configuration tool for Ubuntu is ufw. Developed to ease iptables firewall configuration, ufw provides a user friendly way to create an IPv4 or IPv6 host-based firewall. By default ufw is disabled.

Basic ufw usage

enable UFW:

ufw enable

To check the status of UFW:

ufw status verbose ufw status numbered

Allow ports:

ufw allow 80 ufw allow 443

Allow ports using /etc/service name:

ufw allow http ufw allow https

Allow port/protocol:

ufw allow 53/udp

Allow port ranges:

ufw allow 1000:2000/tcp

Deny (port/protocol):

ufw deny 53/tcp

Delete rules: prepend delete to the rule:

ufw delete allow http
ufw delete deny 53/tcp

Enable/disable logging:

ufw logging on ufw logging off

Allow from IP/subnet:

ufw allow from 192.168.1.1
ufw allow from 192.168.1.0/24
ufw allow from 192.168.1.0/24 to 127.0.0.1 port 445 proto tcp

Deny by IP:

ufw deny from 192.168.1.100
ufw deny from 192.168.1.0/24
ufw deny from 192.168.1.0/24 to 127.0.0.1 port 445 proto tcp

Delete specific rules:

ufw status numbered
ufw delete 7

You can reject instead of deny:

ufw reject 53/tcp

Reasonable default:

ufw default deny incoming
ufw default allow outgoing

Show details:

ufw show raw

Start over again:

ufw reset