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The “server port 16262 closed” message means your Project Zomboid client could not establish the preferred direct UDP connection to the server. The game normally uses UDP 16261 for Steam queries and UDP 16262 for the direct connection. Forward both configured ports to the server computer, allow them through its firewall, then test from another network. Friends may still connect through Steam when direct access fails, so the warning can indicate reduced performance or a different network path rather than a completely unreachable server.
What the port 16262 warning actually means
Project Zomboid attempts a direct UDP connection between players and the host. When that attempt to UDP 16262 fails, the client displays: "WARNING: SERVER HAS PORT %1 CLOSED. PERFORMANCE MAY BE SEVERELY AFFECTED." The message is about the direct path, not necessarily about the whole server being offline.
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Clients try direct connectivity first and can fall back to Steam networking. As a result, a player might join successfully while still seeing the warning. A fallback connection can add routing overhead or produce less predictable latency and synchronization. If nobody can join, the same warning is a stronger indication that forwarding, firewall, or address translation is wrong.
Project Zomboid’s 2022 networking release note defines the defaults this way: the game port, UDP 16261, handles Steam queries; the additional UDP 16262 port handles the direct connection. Both values can be changed in the server configuration, so the numbers in your active settings always take priority over remembered defaults.
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Which ports to open
| Port | Protocol | Purpose | Where to forward it |
|---|---|---|---|
| 16261 by default | UDP | Steam query and game-port traffic | Your server computer’s current private IPv4 address |
| 16262 by default | UDP | Direct client connection intended to avoid unnecessary Steam routing | The same server computer and LAN address |
Use the configured equivalents if you changed either port. Forwarding TCP instead of UDP does not solve this warning. Forwarding only 16262 can also leave the server undiscoverable or incompletely reachable because the query/game port is still missing.
Fix the warning step by step
1. Read the ports from the running server configuration
Open the server’s settings or configuration screen and identify the fields labeled as the game/query port and the direct, additional, or UDP port. Confirm which instance you are starting if you run more than one server. A second instance may use different ports, and a router rule aimed at the first instance will not help the second.
- Record the query/game port, normally UDP 16261.
- Record the direct port, normally UDP 16262.
- Check that the server has actually been restarted after a port change.
- Use these recorded values in every router and firewall rule.
Do not assume the warning’s number is the only value that matters. The client names 16262 because that is the direct port it could not reach, but the server still needs its query/game port configured and reachable.
2. Give the server a stable private IP address
Port forwarding points to a private LAN address such as 192.168.1.25. Most routers assign that address with DHCP, and it can change after a reboot or lease renewal. If the forwarding rule still targets yesterday’s address, the router sends packets to the wrong device even though the rule appears enabled.
- Find the server computer’s current private IPv4 address in the operating system’s network details.
- In the router’s DHCP or LAN section, create a DHCP reservation for that computer’s network adapter.
- Alternatively, configure a static address that is outside the router’s automatic DHCP pool and does not conflict with another device.
- Reconnect or renew the address, then verify that the server still has the reserved value.
A reservation is usually safer than manually typing a static address because it keeps gateway and DNS information supplied by the router while preventing the host address from drifting.
3. Create two UDP forwarding rules
Router menus may call this feature Port Forwarding, Virtual Server, NAT Forwarding, or a similar name. Create one rule for each configured UDP port. Set the external or public port and the internal port to the same number unless your network design deliberately uses a different mapping.
- Select UDP as the protocol.
- Enter the configured query/game port (16261 by default) for the external and internal port.
- Set the destination to the reserved private IPv4 address of the Project Zomboid server.
- Save or apply the rule.
- Repeat the process for the configured direct port (16262 by default), targeting the same address.
Some routers offer a port range. A range covering 16261–16262 can work when both ports use UDP and the destination is identical, but two explicit rules make mistakes easier to spot. Do not forward these ports to a console, another PC, or the router’s own management address.
4. Permit inbound UDP traffic on the host
The router can deliver a packet to the server while the operating system silently discards it. Windows Firewall with Advanced Security uses inbound rules to permit a listening program or a specified TCP/UDP port to receive traffic. Allow the Project Zomboid server process, or allow the two UDP ports on the active network profile.
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- Open Windows Defender Firewall with Advanced Security.
- Select Inbound Rules, then choose New Rule.
- Choose Port, select UDP, and enter the configured port number. Create one rule per port, or enter both numbers where the wizard accepts a comma-separated list.
- Select Allow the connection.
- Apply the rule only to the profiles you use, such as Private; include Public only when that profile is intentional and secured.
- Give the rule a clear name, save it, and repeat for the other port if necessary.
If the server executable already has an inbound program rule, check that the rule is enabled and applies to the current profile. Security suites can install a second firewall, so temporarily disabling only the relevant network filtering component for a controlled test can reveal whether it is blocking traffic; re-enable protection immediately and create a narrow permanent exception instead.
5. Restart and verify that the server is listening
Stop and start the Project Zomboid server after changing ports or firewall rules. A forwarding rule cannot succeed if no process is listening. Confirm in the server console or status output that it started without a bind error and is using the ports you recorded.
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6. Test from outside your home network
A connection from the same LAN can succeed without traversing the router’s public-side rule. Test with a friend on a different internet connection, or use another external network while the server is running. Have the tester join normally and note whether the warning disappears and whether the server is stable during play.
- LAN succeeds, Internet fails: concentrate on forwarding, the destination IP, the host firewall, and upstream NAT.
- Internet join succeeds with the warning: direct UDP 16262 is still unavailable or not being selected; investigate Relay and the path quality.
- Neither LAN nor Internet works: first check that the server is running, listening on the intended ports, and visible to a local client before changing router settings.
Many public port-check websites test TCP only or cannot produce a useful UDP result when an application is not actively listening. An external game-join test while the server is running is more representative for this UDP service.
Check Steam Relay when players can already join
Project Zomboid developer Beard has stated that the closed-port warning can also appear when Use Steam Relay is enabled. Relay networking can allow a session to function even when the direct port is not reachable.
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If you want to evaluate direct connectivity, locate the server’s Steam Relay setting, disable it for a controlled test, restart the server, and have an off-LAN player join. If disabling Relay prevents connections, the direct path is not working and the router or firewall still needs attention. If the server works with Relay enabled and your players experience no practical issue, the warning may be informational for your setup; it does not by itself prove that the server is unusable.
Rule out double NAT and CGNAT
Double NAT from two routers
Port forwarding must pass through every router performing address translation. A common arrangement is an ISP gateway connected to your own router. Forwarding 16261 and 16262 only on the second router leaves the first router with no destination for inbound traffic.
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- Place the ISP gateway in bridge or modem mode, if your provider supports it; or
- Forward both UDP ports from the gateway to your own router’s WAN address, then forward them again from your router to the server’s private address.
Check the WAN address shown by your personal router. If it is itself private, another NAT device is upstream. Coordinate both devices or ask the ISP which device should perform routing.
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Some providers share one public IPv4 address among many customers. Compare the WAN address displayed in your router with the public address visible from an external service. If the router receives a private address or an address in 100.64.0.0–100.127.255.255, it may be behind CGNAT. The latter range is reserved for carrier-grade NAT.
With CGNAT, your router does not control the public-facing translation, so ordinary inbound forwarding cannot create a path to the server. Ask the ISP for a public IPv4 address or a plan that permits inbound connections. If that is unavailable, use a managed game host or another server located on a network with a publicly routable address.
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Home-router forwarding applies only when you host on your own LAN. A managed provider controls the edge firewall and allocates the UDP ports. In that case, check the provider’s control panel for the assigned game/query and direct ports, open those ports in the provider firewall, and confirm that the selected Project Zomboid build is supported. Do not add rules to your home router unless players are connecting to a computer inside your home.
Ask support to confirm whether UDP 16261 and 16262 are available, whether a different mapping is required, and whether an upstream firewall or shared NAT prevents direct inbound traffic. A provider can remove CGNAT and home-router work, but it cannot compensate for an unsupported game build or a misconfigured server instance.
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|---|---|---|
| Mods and files | Maximum control over files, launch options, saves, and mods. | Control depends on the provider’s panel and file access. |
| Public inbound address | Required; CGNAT can make it unavailable. | Usually supplied by the provider, subject to its network design. |
| Networking work | You maintain router forwarding, DHCP reservations, and the host firewall. | The provider maintains edge NAT and firewall rules; you still configure allocated ports. |
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| Build compatibility | You choose when to update and can match your players’ build. | Verify support for the exact Project Zomboid build before moving a save. |
Managed hosting is most useful when the ISP will not provide a public address, the network has unavoidable double NAT, or you do not want to maintain a router and firewall. It is not automatically better for every group: self-hosting offers deeper file and mod control when your connection can accept inbound UDP.
Diagnose changes that have no effect
The forwarding rule looks correct, but the warning remains
- Recheck that the rule targets the server’s current reserved LAN address.
- Compare every router port with the values shown by the running server, not just the defaults.
- Confirm the protocol is UDP and that both ports are present.
- Verify the Windows Firewall rule is enabled for the active network profile.
- Restart the server after editing settings and check for bind errors.
- Compare the router WAN address with an external public address to identify double NAT or CGNAT.
- Test with Steam Relay disabled if the server otherwise works.
Only one of several servers works
Each simultaneously running instance needs its own query and direct ports, and each pair must point to the correct host process. Reusing 16261 or 16262 for two instances creates a bind conflict or sends traffic to the wrong server. Assign unique UDP pairs, reserve the relevant LAN addresses, and advertise the matching port for each instance.
The warning appears after changing an ISP or router
A new router may use a different LAN subnet, erase reservations, or enable a second NAT layer. Recreate the reservation and both forwarding rules, then inspect the new WAN address. If the new provider uses CGNAT, local changes cannot restore direct inbound access without a public-address option or a different hosting arrangement.
A concise verification checklist
- The server is running and listening on the configured query/game and direct ports.
- UDP 16261 and UDP 16262 are forwarded, unless your configuration shows different values.
- Both rules target the same, current server IPv4 address.
- The host firewall permits inbound UDP traffic on those ports and the active profile.
- No second server or application is using the same ports.
- The external test comes from outside the server’s LAN.
- The router WAN address is publicly routable, not private and not in 100.64.0.0–100.127.255.255.
- Steam Relay settings have been tested when joins work but the warning persists.
- A managed host has opened its assigned UDP ports and supports the server’s Project Zomboid build.
What success looks like
After correcting the destination address, forwarding both UDP ports, and permitting them through the host firewall, an off-LAN player should be able to join while the server uses its direct path. If players can join only when Steam Relay is enabled, the underlying server may remain playable, but UDP 16262 is still not directly reachable. Treat that as a network-path limitation and decide whether the resulting latency and synchronization are acceptable for your group.
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