+core.register_on_prejoinplayer(function(name, ip)
+ local auth = core.auth_table
+ if auth[name] ~= nil then
+ return
+ end
+
+ local name_lower = name:lower()
+ for k in pairs(auth) do
+ if k:lower() == name_lower then
+ return string.format("\nCannot create new player called '%s'. "..
+ "Another account called '%s' is already registered. "..
+ "Please check the spelling if it's your account "..
+ "or use a different nickname.", name, k)
+ end
+ end
+end)