Project Zomboid Server Not Showing: Ports, Version and Firewall

1. Check the process and build

Read the console and log through world load. If the process exits, resolve the configuration, Lua, mod or memory error first. Confirm that client and server run the exact same Build 42 branch and version. After a patch, run app_update 380870 validate, restart and update the client too.

Connect locally on the server, then from another LAN device. If LAN access fails, Internet access will fail as well; leave port forwarding alone for now.

2. Check profile, access and discovery

Find the profile selected by -servername. In that INI, Open=true permits joins and Public=true requests public listing. Check PublicName, the player password and whitelist. An RCON password is not a join password.

Direct connection succeeding while browser discovery fails points to listing settings or Steam discovery, not the map. Wait a few minutes after startup and also test the manual IP-and-port entry.

3. Test ports, firewall and router

Current Build 42 defaults use UDP 16261, UDP 16262, and sometimes UDP 8766 depending on Steam networking. Confirm the ports actually configured. Allow the program or these UDP ports through the host firewall. On a home network, give the server a fixed private address and forward the same ports to it.

Test from an external connection, such as a phone with Wi-Fi disabled. A web port checker built for TCP may call a working UDP service closed; a real game-client join is the useful test. With double NAT or carrier-grade NAT, local forwarding is insufficient. Request a public IPv4 address or use a hosted server.

4. Separate mod and security failures

If the client reaches the server and then hangs during download or “Loading Map,” compare WorkshopItems, Mods, dependencies and update versions. Back up first, then test against a copy or a vanilla profile. Do not remove map mods from the production world merely to diagnose it.

Read firewall and server logs at the exact connection time. Seeing no packet at all is different from a logged version rejection. After a fix, repeat LAN, Internet, restart and persistence tests.

The Build 42 installation guide provides a known-good baseline. If your ISP blocks inbound access, compare Project Zomboid servers.