What language to choose for writing a client in a client-server 2D game?

Question

Java

Goal: writing a client-server game (PvP, board game, like chess). On the server side - data processing, on the client side - moving sprites across the playing field. I think to write a server part on Java. I'm not familiar with him, but this project will help you get used to it. I began to teach according to Schildt, while it seems to be more or less clear. And then the questions begin.
On what to write a client part? The requirements are as follows: simple work with 2D graphics and multiplatform. Support for at least Windows and Linux is required, and preferably without developing a separate client for each axis. The answer "on what you can, write on that" is not suitable, because. I can do a little on asma, a little on sharp (no trust in Mono), a little on PureBasic (too primitive, problems in windowed mode are trite with the cursor, there is no user-sprite interaction). The question is open - on what to write the client part.
And the second question is whether there is a ready-made example of a server in Java and a client in a suitable language? For several days I have been trying to figure out the client-server interaction, and I can’t find a normal example so that the client is constantly working and waiting for commands from the server, and the server is constantly working and waiting for commands from the client. An example without any JSON would do, I would just pass regular strings.
The only advice I heard from friends is C++ and Qt. It seems like it would be too difficult. I would like to hear other opinions. Thanks in advance.

Answer 1

Regarding the client - there is a node-webkit.
On it, for example, Game Dev Tycoon is written.
The development of the client will be as close as possible to the development of a web application in JavaScript + HTML + CSS, and then it will be possible to package it into a standalone application.

Answer 2

Well, if you began to write the server in Java, then why not write the client in Java too?

Answer 3

Unity2D plus some turn based multiplayer framework like scoreoid.net