Question Auto start/stop server if players > N

Hello.
Today I would like to talk about such a thing as the automatic launch of servers with a certain number of players on the server.

I have a Kernel that is connected to each server and Bungeecord using the netty channel. And also on each VDS, a program is launched that copies the standard game server and launches it using a command. I ran into the following issues.

1) To run on the VDS server you need to find a free port.
2) Servers start after 15 seconds, and this is a very long time, and the kernel at this time does not see the new server and tries to start even more servers.
3) During these 15 seconds before the server starts. Its port may be occupied by another server.



In general, the question is: how can I start, for example, stop the SkyWars game servers in automatic mode, if the number of players is less than a certain number or more?

I want to do both on Hypixel.

Who does not know there if the number of players in the mode is too large, it automatically starts several more servers.