How to put a local server on a WiFi network?

Question

WiFi

The point is this: let's say there are shared files on the server and there are clients connected to this WiFi network that can download these files as if from a remote server. The trick is that it would be possible to exchange data on a WiFi network without access to the Internet. Is there a solution to this problem?

Answer 1

remove the main gateway at this point

Answer 2

you have the answer in the question itself: the
local one can be perceived as "without access to the global network"
configure access for it only for the wifi network and prohibit everything else