This is just a list of common Linux commands that I use on Ubuntu 20.04.
Show all open TCP sockets:
netstat -ntp
Block all incoming and outgoing ports ( you must open each port you want to use in combination with this ):
sudo ufw deny out 1:65535/tcp sudo ufw deny out 1:65535/udp sudo ufw deny in 1:65535/tcp sudo ufw deny in 1:65535/udp
Open incoming and outgoing port for TCP & UDP ( using port 80 as example ):
sudo ufw allow 80
Open incoming and outgoing port for TCP or UDP only ( using port 80 as example ):
sudo ufw allow 80/tcp sudo ufw allow 80/udp
Open incoming port only for TCP or UDP ( using port 80 as example ):
sudo ufw allow in 80/tcp sudo ufw allow in 80/udp
Open outgoing port only for TCP or UDP ( using port 80 as example ):
sudo ufw allow out 80/tcp sudo ufw allow out 80/udp
Open incoming and outgoing port range ( port ranges must only set TCP or UDP per firewall rule ):
sudo ufw allow 2082:2087/tcp
Open only incoming or outgoing port range ( port ranges must only set TCP or UDP per firewall rule ):
sudo ufw allow in 2082:2087/tcp sudo ufw allow out 2082:2087/tcp