Fix multiplayer on Linux

If you try to join a network game on Linux, you will get this "Connection Error: Invalid Host". To fix it, install DirectPlay via Protontricks.

Short story

If you see this: "Connection Error: Invalid Host", then install DirectPlay with Protontricks.

The installation of Protontricks is distribution specific, and there should be plenty of guides for it.

This guide focuses on steps of DirectPlay installation.

DirectPlay installation

Launch Protontricks.

Select S.T.A.L.K.E.R.: Clear Sky in the "Select Steam app" dialogue, click OK.

In "What do you want to do?" dialogue, check "Select the default wineprefix", click OK.

In "What do you want to do to this wineprefix?" dialogue, check "Install a Windows DLL or component", click OK.

In "Which package(s) would you like to install", find "directplay" entry and check it, click OK.
After this, Protontricks will download and install the package.

When it's done, "What do you want to do to this wineprefix?" will pop up again. Just close it.

Done. You should be able to play the multiplayer mode now.

Invalid key

Keys are obsolete now, you don't need them anymore.
Just delete it from the key input field and leave it empty. Perhaps, you will have to repeat this step every time you launch the game.

Broken main menu [Free bonus section lol]

MSAA on DirectX 10 breaks the main menu.
Disable MSAA via configuration file editing.

In the library, right click the Clear Sky cover and select Manage -> Browse local files.
Open user.ltx file in the _appdata_ folder.

Find r3_msaa line, edit it to look like this:

r3_msaa st_opt_off