Question Me and a friend cannot connect to each others multiplayer servers, but we can both connect to a server hosted by another friend.

Jan 30, 2021
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I am trying to host a server for Minecraft java edition, and all of my friends can join except for one. If that friend tries to host his own server everyone can join except me. If one of the other friends hosts everyone can join but ideally my friend that I can not connect with or I would be hosting. If my friend or I try to join each other we either can't connect at all or we join and the world does not load in and we eventually get kicked. We are primarily concerned about Minecraft java edition, but we have run into the same issue on the bedrock edition of Minecraft as well as Rocket League. We have each tried disabling the windows firewall entirely with no luck, and my friend has tried disabling his router's firewall. Our best guess is it is on my friend's end because the problem has been randomly fixed after he has restarted his router, but it only unfixes itself again randomly a few weeks later. Restarting his router rarely fixes the issue though and there has got to be a better way than just praying that it works. Any help is appreciated.