There is a desire to write a client server chat application for Android

Your question will be closed very soon because the reason will be:

The question gives rise to endless debates and discussions that are not based on knowledge, but on opinions. To get an answer, rephrase your question so that it can be given an unambiguously correct answer, or delete the question altogether.

Nevertheless, I will try to guide you on the right path (in my opinion). In order to make a client-server application, you need to think through several parts this question is: the server, the client (the phone in our case) and how they will interact. Here is an introductory article on the subject. To begin with, I would advise you to look in the direction of Firebase. This service will give you many advantages and you will not need to do a lot of things yourself (if you do not have a lot of experience). Here are the instructions for creating a chat: reference_1, reference_2 I hope it will help in your difficult question.

P.S. In matters related to programming is better not to mention especially the Android Studio IDE like this:

I would like to create the app itself on Android studio

Because your question can be rephrased like this:

I want to make a chair using a hammer, what kind of nails do you recommend to me when creating this chair (for example, a screw nail, etc.) and where to put it then you can put it on.

The example certainly doesn't exactly describe your situation but the logic should be clear. The question will be closed and the reason is simple - you ask a question, but do not give people any information about what you have already found on your question and where you have difficulties. I hope my answer will help you in mastering Android development. Good luck :)