Server Hosting Guide
Create a singleplayer world, choose what colonists and landing place you want, and wait until your colonists get out of their pods.
Save the game, then press escape, and click the Host button on your menu.
Configure your desired settings on the Host window, and click host.
When hosting through Steam, users can just connect through your Steam friends list. With the “direct” option, users should portforward 30502 through UDP.