So, my friend didn't know how to make a modpack so I did it for him. It was a few mods none that are client side. I downloaded the pack with no problem but when him and everyone else tried they got a message saying "This server has mods that require FML/Forge to be installed on the client. Contact your server admin for more details." However, no mods are client side. It is just a train mod, a furniture mod, an essentials mod, and worldedit. How can I fix this?