Nuclear Option Server Not Showing Up or Can't Join (Fixes)

Nuclear Option players find dedicated servers through the in game server list, so a server that is missing from that list is a server nobody can join. This guide works through the causes in the order they usually happen, then covers the join errors players see once they do find it: Invalid version, Timeout, Server full and password problems.

First: is the server actually running?

Check the server log or console for this line:

[DedicatedServerManager] Waiting for Players before loading next map

If you see it, the server started, logged on to Steam and is waiting for players. If you do not, the problem is the server itself, not the list:

• Failed to load DedicatedServerConfig at: the config file has a JSON mistake. Look for a missing or trailing comma, or an unclosed bracket, near the last thing you changed.
• Could not start DedicatedServerManager because Steam failed to init: Steam could not start. On Linux this is usually a missing LD_LIBRARY_PATH. Start the server with RunServer.sh, which sets it to the linux64 folder.
• The log stops at Waiting for Steam Game Server logon...: the server cannot reach Steam. Check the machine's internet connection and firewall for outgoing traffic.

Server running but not in the list

1. Give it a minute

A server that just started needs a minute or two to register with Steam and show up. Refresh the server list in the game after that.

2. The query port is closed

The server list finds servers through the query port, UDP 7778 by default. The game port, UDP 7777, carries the actual game. A home server needs both forwarded on the router and allowed through the firewall. If only 7777 is open, players who know about the server still cannot see it.

You can test the query port from outside your network with a Steam server query tool: enter your public IP and port 7778. Shockfront's own guide suggests this check. If the tool gets no answer, the port is closed or forwarded to the wrong machine.

3. Port changes that never applied

If you moved the server to other ports, check both blocks in DedicatedServerConfig.json:

"Port": { "IsOverride": true, "Value": 27015 },
"QueryPort": { "IsOverride": true, "Value": 27016 }

With IsOverride set to false, the server ignores Value and keeps using 7777 and 7778, so your router forwards the wrong ports.

4. Hidden is on

"Hidden": true keeps the server out of the public list completely. Set it to false and restart, or run reload-config.

5. You are on the same network as the server

If friends see the server but you do not, and you play on the same network it runs on, your router probably lacks NAT reflection (also called NAT loopback or hairpinning). Your own PC cannot reach your public IP from inside. Shockfront's guide points to this as the usual cause. Turn it on in the router if it has the option. Not every router does.

6. Check your own Player.log

The game logs failed server list queries. Open:

%USERPROFILE%\AppData\LocalLow\Shockfront\NuclearOption\Player.log

and search for:

Request Server List, fail index:

The line includes the IP and query port the game tried. If it lists your server with the right address, the game found it in Steam's list but could not query it, which points back to the query port or a firewall.

7. CGNAT

Some internet providers put customers behind carrier grade NAT, where no amount of port forwarding works. If your router's WAN IP differs from the IP websites show for you, that is likely the cause. A hosted server avoids it, see how to host a game server without port forwarding.

Join errors

Failed to join: Invalid version

The server and the player are on different game builds. Nuclear Option is in Early Access and patches often, and every patch needs the server updated too:

steamcmd +force_install_dir <server folder> +login anonymous +app_update 3930080 validate +quit

Then restart the server. Players update the game through Steam. If you run a beta branch on the server, everyone needs the same branch.

Failed to join: Timeout

The player found the server but could not finish connecting. The usual causes are the game port (UDP 7777) being closed while the query port is open, or a firewall on the server dropping game traffic. Check the forwarding for the game port and allow the server executable through the firewall.

Failed to join: Server full

The server is at MaxPlayers. Raise it in the config if your hardware has headroom, keeping in mind the server list shows a performance warning above 16 players. See Nuclear Option server requirements.

Password incorrect

Passwords are compared exactly, so check capitals and spaces. If you changed Password in the config, the new password only applies after a restart or reload-config.

The first join is slow

That is normal. An empty server has no mission loaded, and the first player to join waits while it loads the next mission in the rotation. If a specific mission never loads, check the log for Could not find mission with name, which means a misspelled name in MissionRotation, or Failed to download workshop item for a Workshop mission that is private or removed.

Kicked straight away

Check whether the player is in ban_list.txt or one of the other files in BanListPaths, or was kicked or vote kicked this mission. Kicks last until the server restarts, vote kicks until the next mission, and three vote kicks add an automatic ban. Accounts borrowed through Steam Family Sharing cannot join while the owner of the game is already on the server. The fixes for each are in Nuclear Option server commands.

On GamezServers

Most of this list cannot happen on a hosted server: the game and query ports are opened and set in the config for you, there is no router or NAT reflection involved, and the server updates itself from Steam on every restart. If your server is not in the list:

1. Make sure it is Online in the dashboard. Servers sleep after 4 days with nobody online, and anyone with access starts them again in one click.
2. Give it a minute or two after starting to appear in the list.
3. Search the list for the exact name in Settings > Name and server list.
4. After a game patch, restart the server so it updates, then have everyone update the game.

Still stuck? Email support@gamezservers.com from your account email and we will look at the server's logs with you. Not hosted with us yet? See Nuclear Option server hosting.