Enable or block firewall access
Your system should be equipped with a firewall that allows it to block programs from being accessed by other people on the internet or your network. This helps to keep your computer secure.
Many applications can use your network connection. For instance, you can share files or let someone view your desktop remotely when connected to a network. Depending on how your computer is set up, you may need to adjust the firewall to allow these services to work as intended.
Each program that provides network services uses a specific network port. To enable other computers on the network to access a service, you may need to “open” its assigned port on the firewall:
Go to Activities in the top left corner of the screen and start your firewall application. You may need to install a firewall manager yourself if you can’t find one (for example, GUFW).
Open or disable the port for your network service, depending on whether you want people to be able to access it or not. Which port you need to change will.
Save or apply the changes, following any additional instructions given by the firewall tool.