One of the cool features of steam is that it can download games from other steam clients on the same network. In my case, I have a laptop and a steam deck. As a quick hint, the setting is in the Settings » Downloads section of the Steam Client. Look for

  • Game file transfer over local network
  • Allow transfer from this device to

To allow the ports through the client firewall, activate the steam services. Ideally both as you then can also stream from that device to e.g. your Steam Deck.

firewall-cmd --zone=public --add-service=steam-lan-transfer --permanent
firewall-cmd --zone=public --add-service=steam-streaming --permanent
firewall-cmd --reload

In case they are named different on your system, check the existing services with

firewall-cmd --get-services

Contents of /usr/lib/firewalld/services/steam-lan-transfer.xml

<?xml version="1.0" encoding="utf-8"?>
<service>
  <short>Steam Local Network Game Transfer</short>
  <description>Allow transfer of game files between devices on the local network.</description>
  <port protocol="tcp" port="27040" />
  <port protocol="udp" port="27031-27036" />
</service>

Contents of usr/lib/firewalld/services/steam-streaming.xml

<?xml version="1.0" encoding="utf-8"?>
<service>
  <short>Steam In-Home Streaming</short>
  <description>Steam in-home streaming allows you to play a game on one computer when the game process is actually running on another computer elsewhere in your home. Through Steam, game audio and video is captured on the remote computer and sent to the player's computer. The game input (keyboard, mouse or gamepad) is sent from the player's computer to the game process on the remote computer.</description>
  <port protocol="tcp" port="27036"/>
  <port protocol="tcp" port="27037"/>
  <port protocol="udp" port="27031-27036"/>
  <port protocol="udp" port="10400"/>
  <port protocol="udp" port="10401"/>
</service>