Your server is running, the console looks happy, and yet nobody can join. Nine times out of ten, the problem is a port: not forwarded, forwarded with the wrong protocol, or blocked by a firewall you forgot existed. The tricky part is that most game servers use UDP, and UDP ports are harder to test than most guides admit.
Here’s how to check a game server port properly, step by step, and how to read the results.
TCP vs UDP: why testing UDP is different
TCP starts every connection with a handshake. A port checker sends a connection request, and the server either accepts it (open), rejects it (closed) or ignores it (filtered). Clear answers.
UDP has no handshake. You send a packet and hope. If the port is closed, the server may send back an “ICMP port unreachable” message. If the port is open, the game server may reply, or it may silently ignore a packet it doesn’t recognise. So “no response” can mean open, or it can mean a firewall dropped the packet.
This is why generic port checkers often report game ports as closed when they’re fine: they only test TCP, and your game listens on UDP.
Common game server ports
| Game | Default port(s) | Protocol |
| Minecraft: Java Edition | 25565 | TCP |
| Minecraft: Bedrock Edition | 19132 | UDP |
| Counter-Strike 2 | 27015 | UDP (game), TCP (RCON) |
| ARK: Survival Evolved | 7777–7778, 27015 (query) | UDP |
| Rust | 28015 (game), 28016 (RCON) | UDP, TCP |
| Valheim | 2456–2457 | UDP |
| FiveM | 30120 | TCP and UDP |
| Palworld | 8211 | UDP |
| Terraria | 7777 | TCP |
Always check your server’s own config. Many hosts and panels change the defaults.
Step 1: Confirm the server is listening
Before blaming the network, check that the server process is listening on the port, on the machine itself.
On Windows:
netstat -ano | findstr :19132
On Linux:
ss -tulpn | grep 19132
You want to see the port bound to 0.0.0.0 (all interfaces) or the machine’s LAN IP. If it’s bound to 127.0.0.1, the server only accepts connections from itself. Fix the bind address in the server’s config.
Step 2: Check the machine’s firewall
- Windows: add inbound rules in Windows Defender Firewall for the exact port and protocol. A TCP rule does nothing for a UDP game.
- Linux with ufw: sudo ufw allow 19132/udp. Specify the protocol, or ufw opens both.
- Cloud servers: VPS and cloud providers often have a second firewall in their control panel (security groups or network rules). It blocks traffic before it reaches your machine, and it’s easy to forget.
Step 3: Check the port forward on your router
For home-hosted servers:
- Give the server a fixed local IP (a DHCP reservation in the router).
- Forward the port to that IP, with the right protocol. Choose UDP, or “Both” if the game uses TCP and UDP.
- Make sure you’re not behind double NAT: an ISP modem-router plus your own router. If both do NAT, you need to forward on both, or put the ISP device in bridge mode.
Step 4: Test from outside your network
Testing your public IP from inside your own network is unreliable. Many routers don’t support NAT loopback, so the test fails even when the port is open to everyone else. Always test from outside.
For TCP ports, any online port checker works. For UDP, use a dedicated udp port checker that sends a UDP probe to your public IP and port, then reports what came back. If you have access to another machine on a different network, nmap can do the same:
sudo nmap -sU -p 19132 your.public.ip
Step 5: Read the result correctly
| Result | What it means | What to do |
| Reply received | Port is open and something answered | You’re done. If players still can’t join, check versions and passwords |
| ICMP port unreachable | Packets arrive, but nothing listens on that port | Server not running, wrong port, or forwarded to the wrong machine |
| No response (open or filtered) | Either open and silent, or blocked | Recheck firewall and port forward, then test with the game’s own query |
| TCP closed or filtered on a UDP game | Wrong test | Retest with a UDP check |
For games that support a status query, that’s the definitive test. A Minecraft status ping, a Steam A2S query or a FiveM info request proves not only that the port is open but that the game server answers on it. If the query works from outside, the port is fine.
Still closed? Check these
- CGNAT. If your router’s WAN IP doesn’t match your public IP, your ISP shares your address with other customers and inbound connections can’t reach you. Ask for a public IP or host on a VPS.
- ISP blocks. A few ISPs block common ports on residential plans. Try a different external port mapped to the same internal one.
- The wrong machine. After a router reboot, the server’s local IP may have changed and the forward points nowhere.
- Antivirus suites with their own firewall, separate from the Windows one.
Keep watching it
Ports that work today break after router firmware updates, IP changes and well-meant “security tidy-ups”. Instead of finding out from players, monitor it: a scheduled UDP check or game status query from outside your network tells you the moment your server stops being reachable. FastPing, for instance, offers UDP checks and game-specific status monitors with alerts to Discord, so a closed port gets fixed before your players notice.
