Core Keeper: Can't connect to server — every fix
Fix a Core Keeper dedicated-server connection in the right order. Match the game version, wait for the world to finish loading, join with IP on a hosted server, share the password, and keep console clients off a Steam dedicated box.
If Core Keeper cannot connect, work through these checks in order. Do not delete the world first. The usual miss is joining with a Game ID when the dedicated server is actually listening on an IP.
Stop as soon as one fix works. If you are helping somebody else, test with one player before asking the whole group to retry.
1. Match the client and server versions
The client and dedicated server must run the same Core Keeper build.
Update the player's game
Close Core Keeper, let Steam (or the other PC store) finish the update, and relaunch it.
Update the dedicated server
Stop the server. On berrybyte, Auto Update pulls the current dedicated build on the next start. Restart once after the patch is live.
Compare versions
The version on the title screen must match the version in the server log.
If you do not want to babysit patches, rent a Core Keeper server that updates on start.
2. Wait until the world is ready
Core Keeper writes GameID.txt and starts accepting joins only
after the world has loaded. Connecting during that window returns
Game not found.
Confirm Overview shows running
On berrybyte the process must be running, not still installing.
Read Console
Wait until the log finishes loading the world. A first boot can take a minute.
Retry one client
Test with one PC client. Do not ask the whole group to mash Join while the cavern is still generating.
3. Use Join with IP on a hosted server
berrybyte binds a game port, so players join from Join Game →
Join with IP. A home server started without -port instead
uses Steam Datagram Relay and a Game ID.
Copy the current join target
On berrybyte, copy Server address from Overview. On a
self-hosted relay server, copy the contents of GameID.txt
after this boot.
Pick the matching dropdown
Open Join Game. Switch the dropdown to Join with IP for an address, or leave Join with Game ID for a relay code. Pasting the wrong type into the wrong box is the usual failure.
Do not reuse a code from last week
A Game ID can change when the server regenerates it. An IP changes when the host reallocates the port.
4. Check the UDP ports (direct-IP mode)
Direct-IP mode needs the UDP port passed as -port, commonly
27015, plus 27016. Relay / Game ID mode does not need
player-facing port forwards.
Use the port the server bound
On berrybyte, Overview is the source of truth. Do not assume 27015.
Forward UDP (self-host, direct-IP only)
Every firewall and router between the machine and the internet must allow UDP on those ports.
berrybyte opens the allocated UDP ports for you. Self-hosters who are fighting NAT can rent a Core Keeper server that already has them reachable.
5. Share or clear the password
Hosted Core Keeper servers often ship with a password already set. The join dialog asks for it on a direct-IP connect.
Read the configured password
On berrybyte, open Settings → Game Settings.
Send the exact string, or clear it
Check capitalisation and characters that chat apps rewrite. Clear it for a public test, then restart.
6. Keep consoles and the wrong storefront off this box
PlayStation, Xbox, and Switch cannot join a PC dedicated server. That is a Core Keeper rule.
A Game ID / Steam-relay server is also Steam-only. Epic, GOG, and Game Pass clients need direct IP.
Confirm every player is on PC
There is no console-to-PC dedicated path.
Move non-Steam PC players to Join with IP
If those clients see a crossplay error on a Game ID, the
server is in relay mode. Start it with -port or use a
host that already binds one.
If none of the six fixes worked
Confirm Console finished loading the world. Then check the leftover causes:
- A sleeping or stopped process keeps a Game ID on disk and answers nothing.
- Check steamstat.us if every Steam-relay join failed at once.
- Check berrybytestatus.com.
Frequently asked questions
Why can't I connect to a Core Keeper server?
Match the game version first, then wait until the dedicated process has finished loading the world. On berrybyte, join from Join Game → Join with IP using the Overview address. Share or clear the password. Console clients cannot join a dedicated server.
Do I join a Core Keeper server with a Game ID or an IP?
It depends on how the dedicated server was started. A self-host without -port uses Steam Datagram Relay and a Game ID from GameID.txt. A hosted server that bound a port, including berrybyte, is joined with Join with IP and the Overview address.
Why does Core Keeper say Game not found?
You pasted a Game ID from a previous boot into a server that is now running in direct-IP mode, or the world has not finished starting. Copy the current address or Game ID after this boot, then join again.
Can PlayStation or Xbox join a Core Keeper dedicated server?
No. Console clients cannot join a PC dedicated server. Epic, GOG, and Game Pass players also fail on a Steam-relay Game ID. Direct IP is the path that allows those PC storefronts to connect.
What ports does a Core Keeper dedicated server use?
Direct-IP mode needs the UDP port passed as -port, commonly 27015, plus 27016. Game ID / relay mode does not need player-facing port forwards. berrybyte opens the allocated UDP ports.