How to create a window program that implements computer-to-computer communication with a common interface (JAVA)?

Question

Java

Hello. There was an idea to create a Java program for two users.
1) How to create a server-client connection (in the global network)
2) How to create in general the same interface for two connected users?

Leave literature or articles on the Internet to read and understand. I read Horstman, "Learning Java" ... the process is described there about the local network.