مشکل اتصال به localhost و دریافت داده های json

نمیتونم امولاتور رو به localhost وصل کنم

package ir.xzn.tarahi.test_json_downloader;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONObject;

public class MainActivity extends AppCompatActivity {

    private RequestQueue myRequsetQueue;
private TextView txt;
public final String log_label = "abtin message";

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

    public void onBtnGetDataClicked(View v) {
        myRequsetQueue = Volley.newRequestQueue(this);
JsonObjectRequest jObj = new JsonObjectRequest(Request.Method.GET,
"http://localhost:81/abtin/get_cat.php",
new Response.Listener<JSONObject>() {
                    @Override
public void onResponse(JSONObject response) {
                        try {
                            JSONArray array = response.getJSONArray("cat");
for (int i = 0; i < array.length(); i++) {
                                JSONObject temp = array.getJSONObject(i);
String str = temp.getString("id") + " " + temp.getString("name") + " [" +
                                        temp.getString("amount") + "]";
Log.i(log_label, "error in JSON_downloder() -> " + str);
txt.append(str + "\n");
}
                        } catch (Exception e) {
                            txt.setText("error in download");
}

                    }
                },
new Response.ErrorListener() {
                    @Override
public void onErrorResponse(VolleyError error) {
                        Log.i(log_label, "error in JSON_downloder() -> " + error.getMessage());
txt.setText("error" + "\n");
}
                }
        );
myRequsetQueue.add(jObj);

}
}