I just spend an amazing amount of time getting this to work, and I have seen no known solution for it so far. So, here's mine. It may be outdated now, and may not work for you. I haven't tested it well, but my server booted, and I could log in.
Related problems - https://github.com/MinecraftPortCentral/Cauldron/issues/1657
https://github.com/MinecraftPortCentral/Cauldron/issues/980
Poor SW9876 of Github, I can't message you directly. -.-
Anyways, this is upgrading Ultra Modded Survival Server v1.4.6
http://www.technicpack.net/modpack/details/ultra-modded-survival-pack.266012
