Connecting Chess Engine with a Java program

Question

I wanted to make a 1 player chess game.

The idea is:

• The move made by the player would be displayed on the GUI.
• It is sent to the Chess Engine in its own specific understood form.
• Then the result of the Chess engine would be taken and then made visible on the GUI.

Currently I have made no progress on it and am on a dead end. My current program on Java lets 2 players play with each other. The program manages the rules that have to be followed and which moves are illegal. But for a single player game I wanted an AI for my game that can take inputs and give outputs. I searched online for various open source chess engines like Stockfish. But found nothing about using it in my program.

I tried to work on to create my own engine but it was quite a challenge for me. Hence connecting it with an external AI is the only solution I think there is.

Answer 1

Let's break it down:

• You have a working Java chess board that you can use to move pieces
• You want a chess engine (engine is a more precise term than AI)
• You want to download Stockfish and use it
• You want to invent a new protocol or technology to communicate your chess board with the Stockfish engine

To me, your question is really:

• How to connect an external chess engine such as Stockfish within my own chess GUI in Java?

Useful old posts in this site:

• Chess Engine API
• What is the optimal way to use Stockfish programmatically?

Basically, what you need to do is:

1. You shouldn't invent your own technology, you should study the UCI protocol. http://wbec-ridderkerk.nl/html/UCIProtocol.html is a useful reference. I can get you started, do this:

   1. Download Stockfish
   2. Open Stockfish in a console/terminal, don't double-click on it with your mouse
   3. Type ucinewgame and then go movetime 1000. Do you see Stockfish's move?
   4. Read the protocol specification and learn how to analyze a position, and the output format.

2. Write a UCI output parser. Parse whatever information you want.

3. Use the information to make a move on your chess board.

The only technical difficulty I can see here is to establish a "connection" between your GUI with the engine. This is done by creating a new process, running the engine.

https://stackoverflow.com/questions/2006035/how-to-create-a-process-in-java has information on how to do it.

Once you have the new process, you can establish a simple standard input/output pipeline. https://stackoverflow.com/questions/27081918/java-how-to-send-a-value-to-child-process-using-outputstream has the details. Ask on Stackoverflow if you're not sure.