LilTaz

I recently started a modded Minecraft world to play with my friends (Hexxit 2) after downloading the server pack and extracting it i run the java 1.12.2.jar file to open the command line to see all the logs and actually start the world. Only problem is it doesn't open at all, I open it with JAVA tm platform se, I remember a few years ago doing the same thing but it worked back then where as now it doesn't. I also tried this with the pixelmon mod and it also doesn't work. Any help?