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Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →If Project Zomboid reports that server port 16262 is closed, the client could not establish the preferred direct UDP connection to your server. Open and forward the server’s configured UDP ports—16261 for Steam queries and 16262 for direct connections—then allow them through the host firewall. Friends may still be able to join through Steam Relay, so the warning is not always proof that the server is unreachable, but direct connectivity can improve the connection path and avoid unnecessary relay routing.
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What the “port 16262 closed” warning means
A Project Zomboid client first attempts a direct UDP connection to the server. The default direct-connection port is UDP 16262. If that connection cannot be established, the client displays: “WARNING: SERVER HAS PORT %1 CLOSED. PERFORMANCE MAY BE SEVERELY AFFECTED.” The message describes the failed direct path; it does not by itself prove that the server is offline.
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Project Zomboid can use Steam-based connectivity as a fallback. A player may therefore join successfully while the direct port remains unreachable. In that situation, the warning identifies a networking limitation rather than an immediate failure to host. The practical question is whether you want a direct path and whether players experience latency, synchronization, or join problems.
Project Zomboid developer Beard has explained that this specific message is caused by UDP 16262 not being correctly opened on the server owner’s router or in the server computer’s firewall. The official networking note also says the additional port is intended to improve latency and synchronization by avoiding unnecessary Steam routing.
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Which Project Zomboid ports must be open?
The default values are configurable. Always use the values shown in the server’s current configuration instead of assuming that every installation still uses the defaults.
| Port | Protocol | Default role | What to forward |
|---|---|---|---|
| 16261 | UDP | Game and Steam-query port | Forward to the server computer’s current private IPv4 address. |
| 16262 | UDP | Direct client-connection port | Forward to the same server computer and allow it through the host firewall. |
The official release note describes UDP 16261 as the game port used to handle Steam queries and UDP 16262 as the additional port used for the direct connection. If you changed either value in the server settings, substitute the configured value in every router and firewall rule. Forwarding the remembered defaults while the server listens on different ports will not solve the warning.
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Fix the warning in the correct order
Work through these checks while the server is running. Changing several settings at once makes it difficult to identify the actual fault, so verify each stage before moving to the next.
1. Confirm the server’s actual port settings
- Open the Project Zomboid server configuration you use to start the host.
- Identify the query or game port and the direct UDP port. The normal defaults are 16261 and 16262.
- Write down the exact values, including any custom port numbers.
- Stop and restart the server after changing a port, then verify that the server starts without a bind or port-in-use error.
Router rules and firewall rules must match the ports on which the process is listening. A rule for UDP 16262 has no effect if the server was changed to another direct-connection port.
2. Give the server computer a stable LAN address
Port forwarding sends traffic to a private address on your home network. If that address comes from DHCP and changes, the router can continue forwarding to the old computer or to an address that is no longer assigned.
- Find the server computer’s current private IPv4 address.
- In the router’s LAN or DHCP settings, create a DHCP reservation for that computer, or configure an equivalent static address that does not conflict with the router’s DHCP pool.
- Reconnect the computer or renew its network lease if necessary.
- Confirm that the address shown on the computer is the same address selected as the forwarding destination.
Use the server host’s private IPv4 address, not its public Internet address, in the forwarding rule. If the destination changes later, the rule can silently stop working even though its port numbers still look correct.
3. Forward both UDP ports to the same host
In the router’s port-forwarding, virtual-server, or NAT section, create inbound UDP rules for the configured query/game port and direct-connection port. With default settings, that means UDP 16261 and UDP 16262.
- Set the external or public port to the configured game/query port.
- Set the internal or private port to that same number.
- Choose UDP rather than TCP, or choose a combined TCP/UDP option only if the router does not provide a UDP-only choice.
- Set the destination to the reserved private IPv4 address of the Project Zomboid server.
- Create the equivalent rule for the direct port.
- Save or apply the configuration and confirm that both rules are enabled.
Forwarding only 16262 can leave Steam queries unavailable; forwarding only 16261 can leave the direct path unavailable. The safest default configuration is both UDP ports on the same server computer. If your server uses custom values, forward those values instead.
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4. Permit the ports in Windows Firewall
A router rule controls traffic arriving at your network. The operating system can still discard that traffic before Project Zomboid receives it. Microsoft describes an inbound port rule as allowing any program listening on a specified TCP or UDP port to receive traffic sent to that port.
- Open Windows Defender Firewall with Advanced Security.
- Select Inbound Rules in the left pane.
- Choose New Rule.
- Select Port, choose UDP, and enter the configured Project Zomboid port or ports.
- Choose Allow the connection.
- Apply the rule to the active network profile used by the server computer.
- Give the rule a clear name, save it, and make sure it is enabled.
You can instead allow the Project Zomboid server program itself when your firewall policy is managed by application rules. Whichever method you use, permit the actual UDP ports and check that another higher-priority block rule is not overriding the allow rule. If the computer has a third-party security suite, inspect its inbound-network policy as well.
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5. Test from outside your home network
A connection test from another device on the same LAN does not prove that the Internet-facing rule works. Local traffic may never traverse the router’s WAN interface, and some routers handle internal loopback differently from outside traffic.
- Leave the Project Zomboid server running.
- Ask a friend on a different Internet connection to join, or use another suitable external vantage point.
- Have the tester connect using the server’s public address and the configured game information.
- Record whether the player can join, whether the 16262 warning remains, and whether the result changes after each network adjustment.
UDP checks are meaningful only while the server is listening. A generic port-checking website may not identify a UDP service reliably, so an actual join attempt from another network is the more useful test for this game.
6. Check for double NAT and carrier-grade NAT
Port forwarding requires an inbound-routable public IPv4 address. Compare the WAN address shown in your router with the public address visible from an external connection.
- If the router’s WAN address is private, another router or gateway is performing NAT upstream. That is double NAT. Put the upstream device in bridge mode, forward the ports through both layers, or place the game router in the upstream device’s DMZ only if you understand the security implications.
- If the WAN address is in 100.64.0.0 through 100.127.255.255, the connection is using the shared carrier-grade NAT range cited in port-forwarding guidance. Your router does not have a directly reachable public IPv4 address, so ordinary inbound forwarding may be impossible.
- If the two displayed addresses do not match for another reason, contact the Internet provider and ask whether inbound IPv4 connections are filtered or whether a public address can be supplied.
CGNAT is an ISP-level limitation, not a missing checkbox in the Project Zomboid server. If the provider cannot offer a public inbound address, use a relay-capable setup or consider managed hosting that supplies reachable networking.
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7. Test Steam Relay behavior
The Project Zomboid developer has stated that the warning can also appear when Use Steam Relay is enabled. If the server works and friends can join, temporarily test with that setting disabled when your goal is a direct connection.
- Locate the server’s Steam Relay setting in the configuration you use to launch the server.
- Change the setting only after recording its current value.
- Restart the server so the change is loaded.
- Have an external player join again and compare the warning and connection behavior.
Relay behavior and direct forwarding are separate paths. Disabling the relay does not open a router port, and opening 16262 does not guarantee that a relay setting will be ignored. Treat the warning as informational when players connect reliably and you have no practical performance problem.
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Diagnose the result you get
Players can join on the LAN but not over the Internet
The server process is probably running, so prioritize the Internet-facing path. Recheck the forwarding destination, confirm that the destination address did not change, and verify that both rules use UDP. Then inspect Windows Firewall and any upstream router. A private or 100.64.0.0–100.127.255.255 WAN address points toward double NAT or CGNAT rather than a Project Zomboid configuration error.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsFriends join, but the 16262 warning remains
Successful joins show that a fallback path is available, not that the direct port is open. Check the Use Steam Relay setting and run a fresh external test after changing it. If players experience no noticeable problem, the warning may be informational; if latency or synchronization is poor, continue checking the direct UDP rule and host firewall.
Changing router rules has no visible effect
Verify all three identities: the server is listening on the ports you changed, the router rule targets the current private IPv4 address, and the router has a publicly routable WAN address. A rule aimed at an old DHCP address, a custom server port, or a downstream router will not affect the active server.
Only one of the two ports was forwarded
Complete the pair. UDP 16261 handles the default Steam-query function, while UDP 16262 handles the direct connection. The client can fall back when one path is unavailable, but the missing port explains why the corresponding function does not work as intended.
The server runs on a managed host or rented machine
Home-router forwarding does not apply when the server is hosted in a provider’s network. Check the provider’s allocated UDP ports, external firewall, security group, and public-address policy. Make sure the provider supports the Project Zomboid build you are running and that its assigned ports match the server configuration. If the provider has not allocated 16261 and 16262, use the values it supplies rather than trying to forward your home router’s defaults.
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Self-hosting gives you direct control over server files, mods, configuration, and updates, but it depends on a public inbound address and requires router and operating-system firewall work. CGNAT, restrictive ISP policies, or a permanently changing home network can make that arrangement unreliable.
| Decision factor | Self-hosting at home | Managed hosting |
|---|---|---|
| Mods and files | Full control over local files and configuration. | Depends on the provider’s file access and mod support. |
| Inbound address | Requires a publicly reachable address or a working relay path. | Usually provides a datacenter address, subject to the provider’s network policy. |
| Router and firewall work | You maintain port forwarding, LAN addressing, and host firewall rules. | The provider manages its network edge; you still configure the game server and any provider firewall. |
| Recurring cost | No hosting fee, but your home connection and electricity remain in use. | Requires a recurring hosting payment; current price depends on the provider and plan. |
| Uptime | Limited by your home power, router, ISP, and computer. | Depends on the provider’s infrastructure and maintenance policy. |
| Build compatibility | You choose when to update. | Confirm support for your exact Project Zomboid build, especially when using a newer or experimental branch. |
Managed hosting is a fallback for CGNAT or restrictive networks, not a universal cure. It will not correct a mismatched server configuration or an unsupported game build. Before moving, confirm the provider’s current build support, region, port allocation, pricing, and file or mod controls.
What the warning does—and does not—tell you
- It tells you that the client could not establish the preferred direct UDP connection on the configured direct port.
- It does not identify whether the router, the host firewall, an upstream NAT layer, CGNAT, or Steam Relay caused the failure.
- It does not prove that the server is offline when players can connect through another path.
- It does not justify inventing a performance percentage: no authoritative percentage improvement or success-rate figure has been established for fixing this warning.
Use the external join test and the configuration checks to distinguish an informational warning from a real connectivity problem. The reliable repair is specific: match the server’s current ports, forward both UDP paths to the current host address, allow them through the host firewall, and verify that the Internet connection can accept inbound traffic.
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