import com.corundumstudio.socketio.Configuration;
import com.corundumstudio.socketio.SocketIOClient;
import com.corundumstudio.socketio.SocketIOServer;
import com.corundumstudio.socketio.annotation.OnConnect;

public class SocketIOServerApplication {

    public static void main(String[] args) {
        Configuration configuration = new Configuration();
        configuration.setHostname("localhost");
        configuration.setPort(8080);

        SocketIOServer socketServer = new SocketIOServer(configuration);

        // You need to add a custom namespace and listener here.
        // Do not use the default namespace.
        socketServer.addNamespace("/my-namespace").addListeners(new MyNamespaceListener());
        socketServer.start();
    }

    public static class MyNamespaceListener {
        // Listen for the connect event.
        @OnConnect
        public void onConnect(SocketIOClient client) {
            // Send an event here.
            // The event name is debug and the data is "test".
            client.sendEvent("debug", "test");
        }
    }
}

import io.socket.client.IO;
import io.socket.client.Socket;
import io.socket.emitter.Emitter;

import java.net.URISyntaxException;
import java.util.Arrays;

public class SocektIOClient {
    public static void main(String[] args) throws URISyntaxException {

        // Establish a connection with the socket-io server through the custom namespace.
        Socket socket = IO.socket("http://localhost:8080/my-namespace");

        // Listen for the event named debug.
        socket.on("debug", new Emitter.Listener() {
            @Override
            public void call(Object... args) {
                // Print the args.
                // The args is [debug, test], which contains the event name, but the expected args is [test].
                System.out.println(Arrays.toString(args));
            }
        });

        socket.open();
    }
}

private void onevent(Packet<JSONArray> packet) {
       ...
        if (this.connected) {
            if (args.isEmpty()) return;
            String event = args.remove(0).toString();
            super.emit(event, args.toArray());
        } else {
            this.receiveBuffer.add(args);
        }
    }