Host Firewall Basics
It is recommended to use a simple host firewall and deny any incoming connections on all ports. For a Linux host OS like Debian, Ubuntu and Arch Linux, gufw [archive] provides a simple graphical user interface for the Uncomplicated Firewall [archive] program.  It is easy to perform common tasks like blocking or allowing P2P, individual, or pre-configured ports.
How-to: Install and Configure a Firewall
Although not recommended, it is possible to add special firewall rules, use pre-configured options for common programs and services, or set other advanced options in gufw by following this guide [archive].
For further information on firewalls, see here.