Android Studio – How to receive the message from stomp websocket with spring boot on android?

I’ve got the simple WebSocket example from https://spring.io/guides/gs/messaging-stomp-websocket/

package com.example.chatservice.message;

import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {

    @Override
    public void configureMessageBroker(MessageBrokerRegistry config) {
        config.enableSimpleBroker("/topic");
        config.setApplicationDestinationPrefixes("/app");
    }

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/gs-guide-websocket").withSockJS();
    }
}

@Controller
public class ChatController {
    @MessageMapping("/hello")
    @SendTo("/topic/greetings")
    public Greeting greeting(HelloMessage message) throws Exception {
        return new Greeting("Hello from chat!");
    }
}

and I’d like to receive the Greeting message from the spring server to an android app. I use https://github.com/NaikSoftware/StompProtocolAndroid as a stomp client

package com.example.chatapp;

import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.Button;

import androidx.appcompat.app.AppCompatActivity;

import org.java_websocket.WebSocket;

import ua.naiksoftware.stomp.Stomp;
import ua.naiksoftware.stomp.client.StompClient;

public class MainActivity extends AppCompatActivity {
    private StompClient mStompClient;
    public static  final String TAG="StompClient";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button view = (Button) findViewById(R.id.send_message);
        view.setOnClickListener(e->  new StompTask().execute(""));
    }

    private static class StompTask extends AsyncTask<String, Void, String> {
        private StompClient mStompClient;
        String TAG="LongOperation";

        @Override
        protected String doInBackground(String... params) {
            mStompClient = Stomp.over(WebSocket.class, "http://10.0.2.2:8080/gs-guide-websocket/websocket");
            mStompClient.connect();

            mStompClient.topic("/topic/greetings").subscribe(topicMessage -> {
                Log.d(TAG, topicMessage.getPayload());
            });

            mStompClient.lifecycle().subscribe(lifecycleEvent -> {
                switch (lifecycleEvent.getType()) {

                    case OPENED:
                        Log.d(TAG, "Stomp connection opened");
                        break;

                    case ERROR:
                        Log.e(TAG, "Error", lifecycleEvent.getException());
                        break;

                    case CLOSED:
                        Log.d(TAG, "Stomp connection closed");
                        break;
                }
            });

            return "Executed";
        }
    }
}

and the connection to the

http://10.0.2.2:8080/gs-guide-websocket/websocket

works, because the log shows it’s connected

2022-01-18 14:04:56.486 23717-23752/com.example.chatapp D/LongOperation: Stomp connection opened

but it does not subscribe to the topic:

mStompClient.topic("/topic/greetings").subscribe(topicMessage -> {
    Log.d(TAG, topicMessage.getPayload());
});

because when I set the breakpoint it doesn’t ever hit it.

how can I receive this message?