Firewall window. Can not get a specific program on a local network

I'm trying desperately to make sure that the Windows Firewall allows the UDP connection of a client / server software between two computers connected locally (using a router).

When I try with the server-side and client-side Windows firewall, everything works fine, which indicates that the Windows firewall is the culprit.

I want the server / client to be able to communicate with the client-side and server-side firewall, but everything I've tried has not worked.

What I have tried so far:

-added the executable in "Allow a program or feature via Windows Firewall" on the server side and client side

-i tried to create an incoming rule allowing connections from
all UDP ports using a server-side / client-side specific executable

– tried to disable the Web Agent from Avast Antivirus (server side), the client side should have no 2nd party blocking the connection as it is a new installation.

– tried to allow all incoming connections on the private profile in the "Windows Firewall Properties with Advanced Security on the Local Computer" window, again on the client and on the server (at this point , I tested almost everything)

does anyone have any ideas that could solve the problem?