How to transfer the screen image and sound to other computers on the network?

Question

Computer networks

there are computers on Windows in a grid in one room
, you need to synchronously transmit a picture and sound from one main computer to all the others in
order to make presentations , it is

desirable that everything can be started only from the main computer - so that the slave computers forcibly show what is needed
when all computers are turned on - the main starts the demo mode of its desktop,
but it is permissible that on all other computers it was necessary to first launch the desired application,

it must be just convenient and free

Answer 1

VLC player - insert into the player a link to broadcast on clients.
You can make the link permanent, throw it as a playlist or bat
On the server, for example, you can display the broadcast with OBS. XIBO
- fully automated solution for "signs"

Answer 2

There is such an application for remote access - LiteManager , and, unlike analogues, there is a completely free version, even for commercial use. Restriction - up to 30 computers. Among other things, there is also a demo mode - just what you need.