Sunshine + Moonlight on a Steam Gaming Mode PC

Goal: control a living-room / rack gaming PC (mouse, keyboard, controller, video, audio) from a laptop, without a hardware KVM.

Setup: CachyOS, AMD GPU, booting straight into Steam Gaming Mode (gamescope-session). No desktop compositor is running.

Why Sunshine and not VNC or lan-mouse

Option	Gives you	Works under gamescope?
Sunshine → Moonlight	Video, audio, mouse, keyboard, gamepad	✅ Input goes through /dev/uinput virtual devices, capture through KMS
Steam Remote Play	Same	✅ but the client side needs Steam
lan-mouse / Deskflow	Input only	⚠️ gamescope has an EI socket, but support is hit or miss
VNC (wayvnc)	Video and input	❌ needs a wlroots compositor

Host setup (the gaming PC)

1. Install Sunshine (sunshine package on Arch/CachyOS). It needs cap_sys_admin for KMS capture; the package sets that already.
2. Open the ports to your LAN only:

   sudo ufw allow from 192.168.0.0/24 to any port 47984,47989,47990,48010 proto tcp comment 'Sunshine LAN'
   sudo ufw allow from 192.168.0.0/24 to any port 47998:48000 proto udp comment 'Sunshine LAN'

3. Turn off the tray icon. Gaming Mode has no system tray, and without this setting Sunshine exits right after it starts:

   # ~/.config/sunshine/sunshine.conf
   system_tray = disabled

   The symptom is that the service goes inactive (dead) with exit code 0 and the log ends with Main loop has exited / Couldn't accept incoming connections: Operation canceled.
4. Start it with the session:

   systemctl --user enable --now sunshine

5. Check from another machine:

   curl -s http://gaming-pc:47989/serverinfo | grep -o '<state>[^<]*'
   # <state>SUNSHINE_SERVER_FREE

First login: the “CSRF Protection Error”

When you open the web UI at https://<ip>:47990 from another machine, the first-run welcome page can fail with:

CSRF Protection Error: The request was blocked by CSRF protection…

The web UI only trusts its own default address (localhost), so allow the address you actually use:

csrf_allowed_origins = https://192.168.0.50:47990,https://gaming-pc:47990

Restart (systemctl --user restart sunshine), reload the page, and create the admin user. That redirect to /welcome means no admin user exists yet.

Pairing

1. In Moonlight on the laptop, add or select the host. It shows a 4-digit PIN.
2. In the Sunshine web UI, go to PIN and enter it.
3. Pick Desktop or Steam Big Picture.

Moonlight shortcuts worth memorising

Action	Keys
Disconnect (leave the game running)	Ctrl+Alt+Shift+Q, or controller Start+Select+L1+R1
Release / recapture mouse and keyboard	Ctrl+Alt+Shift+Z
Toggle fullscreen	Ctrl+Alt+Shift+X
Stats overlay	Ctrl+Alt+Shift+S
Quit the app on the host	right-click the app tile → Quit

Gotchas

1. steam -shutdown under gamescope gets respawned within about a second by steam-launcher, so don’t expect Steam to stay closed.
2. AV1 encoding errors in the log (Device does not support encoding av1) are harmless on RDNA2. H.264/HEVC via Vulkan get picked instead.

Related: Battle.net on a Steam Gaming Mode PC