How to play Online with a friend without troubles?

[Henry852]

Hi, I've been playing this game for a few days and it's pretty fun. When I tried to play with a friend in multiplayer, I couldn't—he couldn't join me and I couldn't join him (I was in the game lobby, not the one for connecting via IP). Several “connection terminated” errors or something like that kept popping up. We tried to join each other for quite a while until, somehow, I think I disabled the firewall for 0 AD and my friend did the same—some inbound and outbound rules using CMD—and after one attempt, we still couldn’t play. But then I logged in, and out of nowhere, the game appeared; I registered, and that’s when I managed to join. My friend shut down the server, and when he restarted it, I tried to join again but couldn’t, even because of the firewall thing, and today we tried again, we checked some firewall settings, and it was about some inbound and outbound rules; my friend was missing an outbound rule or something like that, I created it and I couldn’t get into his server, but after a few tries I managed to play with him again; it said something about logging in, and well, we wanted to start the game again but I couldn’t join, so we left it at that. And what I’d like to ask is, what’s causing this problem? Why was I able to join out of nowhere? I feel like it has something to do with the firewall because my friend got an error saying that something was blocking the connection, I think, but I’m not sure. It’s weird. I’ll send photos of the errors. By the way, I tried searching for how to play online or something similar in the forum and didn't find any results, which is why im writing this. If you have a solution for i can play with my friend without problems i would be very grateful, and sorry for my english i used a translator.

[AlexHerbert]

Tienen configurado el puerto en el router?