How to Host a Zandronum Server for Doom Co-op or Deathmatch

To host a Zandronum server, download Zandronum for your system, put an IWAD (Freedoom, or your own doom2.wad) and any PWADs next to it, and start the server with a command like zandronum-server -iwad doom2.wad -file mymod.pk3 -port 10666 +exec server.cfg +map MAP01. Open UDP port 10666 so players outside your network can reach it, and set sv_updatemaster 1 so it appears in Doomseeker. Players need the same Zandronum version and the same WADs, and Doomseeker downloads most community PWADs for them.

Zandronum is light. A co-op or deathmatch server with a few PWADs runs comfortably in 1 GB of RAM, so the work here is mostly files and networking, not hardware.

What you need

• Zandronum from the official download page. Version 3.2 arrived in April 2025, with 3.2.1 as a bug fix release. Use the same version your players run.
• An IWAD. This is the base game data: doom.wad, doom2.wad, tnt.wad, plutonia.wad, heretic.wad or hexen.wad if you own them, or the free Freedoom freedoom1.wad and freedoom2.wad. Commercial IWADs are never downloaded automatically, so every player must own the one you pick. Freedoom avoids that problem for public servers.
• PWADs (optional). Map packs, megawads and gameplay mods as .wad or .pk3 files.
• Doomseeker on your own PC, to find and join the server.
• A connection that accepts incoming traffic. If you are behind CGNAT, forwarding will not work. How to tell if you are behind CGNAT shows the quick check.

Step 1: Set up the server folder

Extract Zandronum into its own folder, for example C:\zandronum-server or ~/zandronum. The Windows download includes zandronum.exe, which runs as a server with -host. The Linux download includes zandronum-server, a console only build meant for servers.

Copy in your files so the folder looks something like:

zandronum-server        (or zandronum.exe)
freedoom2.wad
doom2.wad
zandronum.pk3
eviternity.wad
server.cfg

Keep file names in a consistent case. Linux treats Doom2.wad and doom2.wad as different files, and a wrong case is the most common reason a server says it cannot find a WAD.

Step 2: Write a server config

Create server.cfg with the basics:

sv_hostname "Friday Night Eviternity Co-op"
sv_motd "Be nice. Saves are per map."
sv_website ""
sv_maxclients 12
sv_maxplayers 8
sv_rconpassword "ChangeThisToSomethingLong"
sv_updatemaster 1
sv_broadcast 0
cooperative 1
skill 3
sv_maprotation 1
addmap MAP01

• sv_maxclients is everyone connected including spectators, sv_maxplayers is how many can actually play.
• sv_rconpassword enables remote admin. Leave it empty to manage only from the server console.
• sv_updatemaster 1 registers the server with the master list so Doomseeker shows it.
• cooperative 1 sets the game mode. Use deathmatch 1, teamplay 1, ctf 1, survival 1 or invasion 1 for others.
• skill runs from 0 (I'm Too Young to Die) to 4 (Nightmare!).

For a password protected server, add sv_password "secret" and sv_forcepassword 1. Every setting in this file, plus dmflags and map rotation, is covered in detail in Zandronum server settings explained.

Step 3: Start the server

On Linux:

./zandronum-server -iwad doom2.wad -file eviternity.wad -port 10666 +exec server.cfg +map MAP01

On Windows:

zandronum.exe -host -iwad doom2.wad -file eviternity.wad -port 10666 +exec server.cfg +map MAP01

Several PWADs go after one -file, in load order: -file maps.wad gameplay.pk3. Load order matters for mods that patch other mods, so follow the mod's own instructions.

Run it inside screen or tmux on Linux so it keeps going after you log out. When the console reports that UDP is initialized and the map has loaded, the server is up.

Doomseeker can also start a server for you from its Create Game window, which is a decent way to try settings before you write your own command line.

Step 4: Open UDP 10666

Zandronum uses UDP, port 10666 by default. Each extra server on the same machine needs its own port, usually 10667, 10668 and so on.

1. Allow the port in the firewall. Windows: netsh advfirewall firewall add rule name="Zandronum" dir=in action=allow protocol=UDP localport=10666. Linux with ufw: sudo ufw allow 10666/udp. See Linux firewall for game servers if you use firewalld.
2. Reserve the server's local IP in your router.
3. Forward UDP 10666 to it. The port forwarding guide covers the general steps.

Step 5: Join and test

1. Put the same IWAD in your own Zandronum folder.
2. Open Doomseeker and refresh. Find your server by name and double click it. Doomseeker's Wadseeker fetches missing community PWADs on the way in.
3. Or open the Zandronum console and type connect your.public.ip:10666.

From inside your own network, connect with the local IP, because many routers do not loop the public IP back. If the server never shows in Doomseeker or players cannot join, Zandronum server not showing in Doomseeker works through the causes.

Running a megawad night

Co-op through a megawad is what most private Zandronum servers end up doing. A few habits make it smoother:

• Pick the start map with +map so you can resume next week where you left off.
• Keep players to 8 or fewer on classic maps. Vanilla maps were built for one player and get crowded fast.
• Set sv_maxlives with survival 1 if you want a lives system, or leave it in plain co-op for unlimited respawns.
• Upload WAD updates as new file names, like eviternity2-v2.wad, so players with the old copy are not stuck on a mismatch.

The easier route

For a weekly co-op night a home PC is workable, but someone has to leave it running, deal with the router and keep the WADs in sync. A GamezServers Zandronum server has its own address with the port already open, Freedoom installed so it runs before you upload anything, and panel fields for the IWAD, PWADs, max players, skill, start map and every dmflags and compatflags value. Upload WADs through the file manager or SFTP, edit zandronum.ini in the browser, and run admin commands from the live console. If your group shares it, split the bill so each person pays their part. Looking for other old school shooters to host too: see the best retro shooters you can still host.

FAQ

What port does a Zandronum server use?

UDP 10666 by default, set with -port. Forward UDP, not TCP.

Do my players need to buy Doom II?

Only if your server uses doom2.wad. A Freedoom server needs no purchase, since Freedoom is free to download.

How do players get the PWADs?

Doomseeker downloads most community PWADs automatically when joining. For files it cannot find, set sv_website to a page with direct download links or share them yourself.

Can I run Heretic or Hexen on Zandronum?

Yes. Use heretic.wad or hexen.wad as the IWAD. Every player needs their own copy.

How much RAM does a Zandronum server need?

1 GB covers co-op or deathmatch with a few PWADs, 2 GB a full server running a big megawad or gameplay mod, and only very heavy mods need more.