I made a world on Superflat (Singleplayer) so that after I completed it, I would put it online to play with my friends. Whilst creating it I'd play it on peaceful and creative mode (no problems).
Anyway, having completed this world, I put it up.
The world is meant to be a PvP battleground type thing and therefore It would have to be played it on a difficulty which isn't 0 (Peaceful) so that players' health doesn't regenerate.
I disabled monsters, yet despite doing that, the world is still infested with slimes - which is really inconvenient.
I realised that slimes (strangely enough) don't count as monsters and can't be disabled in Server Properties, so I found a mod that would remove them from Singleplayer or Multiplayer.
It instructed me to put a single file into my Minecraft_Server.jar; only to realize I don't have a .jar in my Minecraft Server file?
If anyone knows how and where I can find/get the Minecraft_Server.jar file, I'd really appreciate it. The slimes are really making my world almost unplayable!