How to send uci messages from c# app to stockfish on android?

Question

I downloaded the binary of Android Stockfish arm64-v8a and looked in the CPP source files. In main() there is all initialization, and then there is UCI::loop(), which catches standard input with getline() and writes back with sync_cout(). How can I write to the engine from a c# (xamarin) application? And is it necessary to make some additional initialization?

I found this, which could be close to my problem, but maybe it is not. I don't want to spend three days just to see I'm doing complete nonsense.

Also I don't know how to recognize Stockfish's console. Is there only one console, no matter how many different libraries the program can use?

As I don't understand the technical part much, I'm including a screenshot of what I expect to be the Stockfish I should communicate with :-). If it is wrong from the beginning, please let me know.

EDIT: What file type is the stockfish-8-arm64-v8a, is it android native library or native shell executable or something else? Where to put the file, how to set it up (in Visual Studio 2015), how to call it from code? I have some code that I tried here but still I can't make it work.

Answer 1

When you're using C#, you can use any UCI engine in the same manner. With C# you have to add an event handler to the OutputDataReceived event (and optionally the ErrorDataReceived event). As a quick example:

ProcessStartInfo si = new ProcessStartInfo() {
    FileName = uciPath,
    UseShellExecute = false,
    CreateNoWindow = true,
    RedirectStandardError = true,
    RedirectStandardInput = true,
    RedirectStandardOutput = true
};

myProcess = new Process();
myProcess.StartInfo = si;
try {
    // throws an exception on win98
    myProcess.PriorityClass = ProcessPriorityClass.BelowNormal;
} catch { }

myProcess.OutputDataReceived += new DataReceivedEventHandler(myProcess_OutputDataReceived);

myProcess.Start();
myProcess.BeginErrorReadLine();
myProcess.BeginOutputReadLine();

SendLine("uci");
SendLine("isready");
SendLine("ucinewgame");

And the methods alluded to above:

    private void SendLine(string command) {
        myProcess.StandardInput.WriteLine(command);
        myProcess.StandardInput.Flush();
    }

    private void myProcess_OutputDataReceived(object sender, DataReceivedEventArgs e) {
        string text = e.Data;
        //Debug.WriteLine("[UCI] " + text);
    }

This is an incredibly simplified example. In my own code I have a semaphore in order to fully process each output line before moving on to the next one and several semaphores in the UCI start and "isready" handling.

For a full overview of the UCI protocol, check out the specification.

Answer 2

You're using the compiled Stockfish binary so you don't need to worry anything about C++. You only need to think about C++ if you're compiling the Stockfish source code yourself (but you're not).

The link you have is about calling a DLL in C# - this has nothing to what you want to do. The Stockfish program you have is independently compiled, and has nothing to do with Microsoft's DLL implementation.

You're looking for this:

https://stackoverflow.com/questions/4291912/process-start-how-to-get-the-output

You should start a new engine process, run it and communicate with the engine by UCI protocol.

EDIT:

I see you have started +100 bounty, but I think it's a mistake. I believe my answer is accurate but I'm unable to debug your environment. Your problem is the unknown file path. Have you added a text file, and try to read it in your app? If you can't load a text file in your program, you can't start a chess engine. Please give a go.

• Save a new text file to where you have the Stockfish engine
• Try to read the text file
• You may want to do it on a simulator. On your PC simulator, you can use path like C:\Engine\SF_engine.

Your technical difficulty has nothing to do with chess engine or UCI protocol, and thus off-topic here.

Answer 3

Finally I made it work with big help of @SmallChess and @Andrew. The first problem came with file stockfish-8-armeabi-v7a with no extension and not much informations about. That's why I asked here. The answer by SmallChess was precise, I just couldn't make things work and I couldn't confirm it for very long time. I run into various problems, more or less easy to deal with, but this one took a lot of time:

I correctly copied the file to folder of my application, but I didn't have permission to run it.

So I had to change it with

string[] cmd = { "chmod", "744", Path.Combine(strToFolder, fileName) };
Java.Lang.Runtime.GetRuntime().Exec(cmd);

and things started to be very easy from now, as Andrew's answer provides fully functional code, which would take also a lot of time to write with not much understanding of the problem, so big thanks to him too.