Which server architecture is better to choose for a client-server application on android?

Question

Java

I wrote my own small server for an Android application, I didn’t use almost anything, I just passed strings via a socket in json format and images in bytes. Then I went through the Internet and found the Restful architecture, but I don’t quite understand how to work with its API. You can suggest high-quality materials that will help Restful understand or advise something else. Thanks in advance.