Getting kicked from our Realm server.

Hello, 

So me and my cousin are at lan. We wanted to play minecraft, so we bought a Realm to play on. But we are getting kicked all the time. 
It keeps on saying; 
"Internal Exception: Java.io.IOException: En eksisterende forbindelse blev tvangsafbrudt af en ekstern vært" 
Det sker inde for 3 sekunder, så det er svært at komme igang med at spille.