Improved Lan System

This mod adds the command /closelan, which allows closing the LAN server without needing to restart the world, and the command /lan, which allows starting the LAN mode. This command takes three mandatory arguments: the gamemode (true or false) to enable or disable cheats, and the port number (a number between 0 and 65536, preferably non-rounded numbers like 20000 or 20010, etc.).

Now you only need to download this mod on the server side, which means only the world you're connecting to needs it installed, the clients no longer need to install the mod.