A client-server application on Java sockets only works if run on the same computer, what's the problem?

Question

Java

I wrote a server in Java, its purpose is to process incoming client requests and return a result, from the client side, the connection to the server is made using an IPv4 address. When I run both the application and the server on the same device, on the same network, everything works. When the server is on one, the client is on the second - zero response.