Ubuntu UFW fules for uPnP client

I'm trying to use VLC on Ubuntu PC to access minidlna on Raspberry Pi.

uPnP seems requires bi-directional UDP.

minidlna will listen to UDP packets at port 1900 and also reply with source port 1900.

So, to allow VLC to receive reply from minidlna, we have to allow UDP packets from source port 1900.

> sudo ufw allow from 192.168.0.0/24 port 1900 proto udp

Ubuntu UFW app profile for Steam Link Game Streaming

I've recently tried Steam Link to stream game to my Android device but quickly found out it was blocked due to UFW firewall.
I've found this GitHub issue and UFW settings: https://github.com/ValveSoftware/steam-for-linux/issues/4803#issue-200408537
To make it convenient, I've created an app profile file to be placed in /etc/ufw/application.d/ folder so that we can easily added or removed from ufw.

Here's the steps:

1. Create a text file /etc/ufw/application/steam_link with the following content:

[SteamLink]
title=Steam Link
description=Steam Link Game Streaming
ports=27037/tcp|27031/udp|27036

2. After the file is saved, it should now appear in the list with "ufw app list" command. For example:

$ sudo ufw app list
Available applications:
  CUPS
  OpenSSH
  Postfix
  Postfix SMTPS
  Postfix Submission
  SteamLink


3. To allow the new steam link application rule, I use the following to command to only allow it on my local LAN:

$ sudo ufw allow from 192.168.0.0/24 to any app SteamLink
Rule added

$ sudo ufw status
Status: active

To                         Action      From
--                         ------      ----
OpenSSH                    ALLOW       192.168.0.0/24           
SteamLink                  ALLOW       192.168.0.0/24