Minecraft wiki entry for Setting_up_a_server, associated text: A: Turning off your firewall on your router/modem means you essentially disabled port forwarding. Port forwarding is actually a subset of firewall rules. If no rule exists on that port (for example 25565), the firewall will ignore/drop the connection attempt (hence, you get a connection timed out). If there is a rule, it should pass on the connection to whatever computer is configured to receive the initial connection attempt.