Channel.push is not working

[SPrio-kt]

My channel.ex file:

  def handle_in("locations", _payload, socket) do
    broadcast!(socket, "locations", %{ping: "succeed"})
    {:reply, {:ok, %{ping: "succeed"}}, socket}
  end

My MainActivity.ex

package com.example.phoenix_channel_test;

import androidx.appcompat.app.AppCompatActivity;
import org.phoenixframework.channels.*;

import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.fasterxml.jackson.databind.node.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.ObjectNode;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    Socket socket;
    Channel channel;
    private Button start;
    private TextView output;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        start = (Button) findViewById(R.id.start);
        output = (TextView) findViewById(R.id.output);

        start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Uri.Builder url = Uri.parse( "ws://192.168.1.4:4000/socket/websocket" ).buildUpon();
                try {
                    socket = new Socket(url.build().toString());
                    socket.connect();
                    channel = socket.chan("user_location:lobby", null);
                    channel.join();
                    ObjectNode node = new ObjectNode(JsonNodeFactory.instance);
                    channel.push("locations", node); // this line is not working

                    channel.on("locations", new IMessageCallback() {
                        @Override
                        public void onMessage(Envelope envelope) {
                            System.out.println("NEW MESSAGE: " + envelope.toString());

                        }
                    });

                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        });
    }
}

In MainActivity.java this line channel.push("locations", node); should respond to the function in channel.ex

  def handle_in("locations", _payload, socket) do
    broadcast!(socket, "locations", %{ping: "succeed"})
    {:reply, {:ok, %{ping: "succeed"}}, socket}
  end

But it is not working, Can anyone please help me out !