Port Forwarding troubleshooting guide

Technical Support
1

Unable to Join Server or server not visible – Simple Troubleshooting Guide

Before starting:

  • Make sure the game server is running in AMP
  • Make sure you are using the correct server IP and port
  • Verify the server is listening on the correct protocol:
    • TCP
    • UDP
    • or both TCP & UDP

1. Check Your Public IP Windows

Open in browser:

myip.is

Check Public IP Linux

Run:

curl -4 -s https://api.ipify.org

2. Configure Port Forwarding

In your router:

  • Forward the game server port to the local IP address of the machine running the server
  • Use the correct protocol:
    • TCP
    • UDP
    • or TCP & UDP

Example:

  • Server PC local IP: 192.168.1.50
  • Game port: 27015

Forward:
27015 → 192.168.1.50

3. TCP Port Testing

TCP ports are easy to test because they return a response.

Test Steps

Open:

https://dnschecker.org/port-scanner.php

Enter:

  • Your public IP
  • Your TCP port

Press:
Check

Expected Result

You should see:

Open

If you see anything else:

  • Port forwarding is incorrect
  • Firewall is blocking the port
  • Server is not running
  • ISP may be blocking the port (CGNAT etc, very possible situation if you have never hosted anything ever)

4. UDP Port Testing

UDP ports are harder to test because they usually do not respond directly.

Recommended UDP Testing Method (Linux)

The best way to test UDP is monitoring incoming packets directly on the server.

Install tcpdump

sudo apt install tcpdump

Monitor UDP Traffic

sudo tcpdump -i any udp port YOUR_PORT

Example:

sudo tcpdump -i any udp port 27015

When that command is running open tool like:

Enter in to it your public IP and UDP port and press Scan Now.

Result

If port forwarding works, you will see incoming UDP packets in the terminal.

If nothing appears:

  • Port forwarding is incorrect
  • Firewall is blocking traffic
  • ISP may be blocking the port
  • Server is not listening on the port

5. Firewall Checks

Only do these checks if the port tests above fail.

Windows Server

Windows Firewall Testing

Temporarily disable Windows Firewall and test again.

If it works afterward:

  • Create a proper firewall rule
  • Re-enable the firewall

Linux Server

Firewall Checks

Make sure firewall tools are not blocking the port and disable temporarily if required. Test again. (Personally these have not caused any issue to me so far)

  • ufw
  • firewalld
  • iptables

Example for UFW:

sudo ufw status