Project Zomboid Server Ports (16261 and 16262 UDP) and How to Open Them
A Project Zomboid server uses two UDP ports: 16261, which players connect to, and 16262. If you run it at home, you have to open both on your router and let them through the firewall. For playing with Host and Steam invites you usually don't need to, and on a rented server they're already open.
The two ports and what each one is for
16261 UDP (DefaultPort in the .ini): the server's port, the one you type when you add it under “Favorites”. 16262 UDP (UDPPort): the second port the server uses. You need both, and both are UDP, not TCP.
You change them in the .ini or when starting the server with -port and -udpport. RCONPort (RCON, for sending commands from outside) only needs opening if you use RCON, and it's TCP. Old guides that talk about opening one port per player or long port ranges are from old versions: these two are enough.
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Opening the ports on your router
Fix the PC's IP
On the server PC, open a command prompt, type ipconfig and note the “IPv4 Address” (something like 192.168.1.40). On the router, reserve that IP for that PC (usually called “static IP”, “DHCP reservation” or similar) so it doesn't change.
Log in to the router
In your browser, go to the “Default Gateway” that ipconfig showed (often 192.168.1.1), with the username and password on the router's sticker.
Create the forwarding rule
Under “Port forwarding”, “NAT” or similar, add a UDP rule from 16261 to 16262 pointing to the PC's IP. If the router asks for ports one at a time, make two rules.
Give your friends your public IP
The one you see on any “what is my IP” website, with port 16261. Heads up: at home it usually changes now and then.
Windows Firewall
The first time you start the server, Windows asks whether to let it use the network: say yes, on public networks too if it asks. If you said no, go to “Windows Defender Firewall” → “Advanced settings” → “Inbound Rules” and create a UDP port rule for 16261-16262.
The .ini also has a UPnP option, with which the server tries to open the ports by itself on routers that support it. If it works, you skip the router step; if not, do it by hand.
If your ISP uses CG-NAT
Some internet providers share a single public IP between many customers (CG-NAT). You can tell because the IP your router shows isn't the one a “what is my IP” website shows. In that case, however many ports you open, nobody can reach you from outside.
Ways out: ask your provider for your own public IP (some do it for free, others charge for it), play with Host via Steam invites (or with Steam Relay when connecting; the three ways to play with friends), set up a private network with Radmin VPN or Hamachi, or host the server outside your home.
Several servers on the same PC
Each server needs its own pair of ports: the second one, for example, 16263 and 16264, with its own .ini (or -port and -udpport) and its own router rule. Players type the port of the one they want.
Checking it can be reached from outside
The most reliable test is a friend trying to join from their home: from inside your own network, many routers won't let you in through the public IP even when everything is fine. You can also try our free tool to check whether a Project Zomboid server is online: enter the address and port and it tells you whether it responds.
On NapNodes
There's nothing to open: the ports are already open. Bear in mind that each server has its own two ports, between 16261 and 16660, so yours may not be 16261. The address and port to play are on the “Address to play” card in the panel and in the “ready” email: type them exactly as shown under “Join” → “Favorites”.
You don't need RCON: commands are typed in the panel's “Console”.
Frequently asked questions
What ports do I need to open for a Project Zomboid server?
16261 and 16262, both UDP. They're DefaultPort and UDPPort in the server's .ini.
Are Project Zomboid ports TCP or UDP?
UDP. Only RCON, if you use it, goes over TCP.
Do I need to port forward to play with Host?
Usually not: your friends join through Steam invites. If they can't connect, try Steam Relay or open 16261 and 16262 UDP.
Why doesn't my NapNodes server use port 16261?
Because each server has its own pair of ports, between 16261 and 16660. Yours is shown on the “Address to play” card in the panel.
I've opened the ports and my friends still can't join
Check that the rule is UDP and points to the PC's current IP, that Windows Firewall lets the server through and that your provider doesn't use CG-NAT (the router's IP has to match the one you see on the internet). If all of that is fine, it's the version or the mods: can't connect to my server.
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