Players cannot join from other computers to my session

Hi guys,

I’m not very experianced with UE4 yet, but I’m asking about the problem with joining sessions. I made a demo project and set it to multiplayer followed by this tutorial: Unreal Engine 4 | Server browser | Host & Join Session | SESSION SERIES - YouTube . Wen I finished, I tested it on my computer by opening 2 demos. On the first one I was hosting a session, on the other on I was trying to join, and it worked. Later I sent the project to my friend so he can try to join or host a session. He was able to host a session but unable to join my created session which was allready running on my computer.

If anyone has a solution to this problem, please post, and thanks again!