Symptoms: Could not connect to a default or fallback server, Server closed, proxy connection error

Possible Causes

  • The backend (lobby/survival) server is not running
  • The wrong address or port is defined in the BungeeCord config.yml
  • A firewall is blocking traffic between the proxy and the backend server

Step-by-Step Fix

Step 1

Check whether the backend servers are running

bash
ps aux | grep java

Step 2

Verify the server addresses in the BungeeCord config.yml

bash
grep -A 5 "servers:" config.yml

Step 3

Check the bungeecord: true setting in the backend servers' spigot.yml

bash
grep bungeecord spigot.yml

Step 4

Test the connection between the proxy and the backend

bash
nc -zv 127.0.0.1 25566

Step 5

Make sure online-mode=false is set in the backend servers' server.properties

bash
grep online-mode server.properties