DayZ Server Query Port: Why Your Server Looks Offline on 2302

You copy your server address out of the launcher, paste it into an uptime monitor, and the monitor says the server is down. Meanwhile forty people are on it, killing each other over a can of beans.

The server is fine. You are knocking on the wrong door by exactly one.

Two ports, two jobs

A DayZ server opens more than one UDP port, and they do different things.

• 2302 - the game port. It carries gameplay traffic for connected clients and does not answer status requests from strangers.
• 2303 - the query port, normally the game port plus one. This is what the server browser talks to, and it is the only port that will tell an outsider anything about the server.

Everything a player sees in the browser - name, map, player count, ping - arrives over the query port. The game port stays silent by design: it has no reason to answer traffic from someone who has not joined.

So a check against 2302 fails on a perfectly healthy server. Not because the server is broken, but because nothing there was ever going to reply.

Where the offset comes from

DayZ inherits its networking from the Arma lineage, and that lineage has always used a small block of consecutive ports rather than a single one. The convention is straightforward: the query port sits one above the game port. Community servers keep the same relationship on custom numbers - a server on 2402 answers on 2403, one on 27016 answers on 27017.

This is worth internalising, because the number you are given is almost always the game port. Server lists show it. Launch parameters use it. Your host puts it in the welcome email. The port that actually answers a monitor is rarely written down anywhere.

What a correct check looks like

Point the check at the query port and use UDP. A live DayZ server replies with a description of itself:

name    [EU|UA] WAU Livonia PVE
map     enoch
players 5/30

That reply is the evidence. On UDP there is no handshake, so silence proves nothing on its own - a firewalled port, a crashed process and a typo in the address all look identical. Only an answer means the server is alive.

Our own DayZ server status checker handles the offset for you: if the port you enter stays quiet, it retries on port + 1 before reporting anything. Paste the address exactly as your host gave it and the check finds the right port on its own.

Firewall rules people forget

On a self-hosted box the query port needs its own inbound rule. Opening 2302 and stopping there is the most common self-inflicted version of this problem: players can connect if they already know the address, but the server never appears in the browser, and every monitor you point at it says down.

The symptom is distinctive. If your server works for people who type the address manually but is invisible in the server list, the query port is closed.

Restarts are not outages, but they look like them

Most DayZ servers restart on a schedule - every three or four hours is typical - to clear vehicles, respawn loot and keep memory usage sane. During that window the server genuinely does not answer, and a monitor will correctly record it as down.

That is not noise to be silenced. It is worth seeing, because it lets you tell the difference between the two-minute gap you scheduled and the twenty-minute gap that means a restart failed and nothing came back up. Set the alert threshold above your normal restart window rather than turning the check off.

What to monitor, concretely

• Protocol UDP, query port - 2303 for a default server, game port + 1 for anything custom.
• Treat silence as down. On UDP a reply is the only honest signal.
• Check from more than one country. DayZ communities are regional; a route that breaks between one continent and your host is invisible from a single vantage point.
• Watch the gap length, not just the state. A four-hour rhythm of two-minute gaps is your restart schedule. A gap that outlives it is an incident.
• Alert somewhere you actually read. Most admins learn about outages from Discord. An email or Telegram alert arrives sooner and does not require someone else to notice first.

The short version

• DayZ answers status queries on the game port plus one: 2303 for a standard 2302 server.
• The game port never replies to outsiders, so checking it always reports down.
• Open the query port in the firewall separately, or your server stays invisible in the browser.
• Scheduled restarts show as short outages - set thresholds around them instead of ignoring the check.