NetworkUtility.shouldRetryException: Unexpected response code 403

Question

excuse me, for the first it works fine, when I click "Tambah data/add data" its force close all of sudden, when I check on logcat it's showing this

NetworkUtility.shouldRetryException: Unexpected response code 403 for http://10.0.2.3/folder_kerja/koneksi.php

koneksi.php was made on separate file, I was trying to connect through MySQL.

could you help me please?

Here's the code

package com.example.a2011500069_dwizahranf2

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.*
import com.android.volley.*
import com.android.volley.toolbox.*
import java.net.*
import androidx.recyclerview.widget.*
import org.json.*


class MainActivity : AppCompatActivity() {
    private lateinit var url: String
    private lateinit var sr: StringRequest
    private lateinit var rq: RequestQueue

    private lateinit var rvAlumni: RecyclerView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        title = "E-Book Alumni Universitas XYZ"

        rvAlumni = findViewById(R.id.rvAlumni)
        val btnTambah = findViewById<Button>(R.id.btnTambah)

        rvAlumni.setHasFixedSize(true)
        rvAlumni.layoutManager = LinearLayoutManager(this@MainActivity)


        btnTambah.setOnClickListener {
            startActivity(Intent(this@MainActivity, EntriAlumniActivity::class.java))
        }
    }

    private fun getDefaultGateway(): String? {
        var defaultGateway: String? = null
        try {
            val enumNetworkInterface = NetworkInterface.getNetworkInterfaces()
            while(enumNetworkInterface.hasMoreElements()) {
                val networkInterface = enumNetworkInterface.nextElement()
                val enumInetAddress = networkInterface.inetAddresses
                while(enumInetAddress.hasMoreElements()) {
                    val inetAddress = enumInetAddress.nextElement()
                    if(inetAddress.isSiteLocalAddress) defaultGateway = inetAddress.hostAddress
                }
            }
        } catch (_: SocketException) {
            defaultGateway = null
        }
        return defaultGateway
    }

    override fun onStart() {
        super.onStart()
        val ipSebelumnya = ip
        if (getDefaultGateway() != null) {
            try {
                for (i in 0..255) {
                    val kepalaIp =
                        getDefaultGateway()?.substring(0, getDefaultGateway()?.lastIndexOf(".") ?: -1)
                    val ipTemp = "$kepalaIp.$i"
                    url = "http://$ipTemp/folder_kerja/koneksi.php"
                    sr = StringRequest(Request.Method.GET, url, {
                        if (it.isNotEmpty()) {
                            ip = ipTemp
                            if(ip != ipSebelumnya) {
                                Toast.makeText(
                                    this@MainActivity,
                                    "Terhubung ke $ip",
                                    Toast.LENGTH_SHORT
                                ).show()
                            }
                        }
                    }, null)
                    rq = Volley.newRequestQueue(this@MainActivity)
                    rq.add(sr)
                }
            } catch (_: Exception) {
                ip = "10.0.2.2"
            }
        } else ip = "10.0.2.2"
        tampilData()
    }
    override fun onResume(){
        super.onResume()
        tampilData()
    }
    private fun tampilData(){
        val listAlumni = arrayListOf<Alumni>()
        val adapter = AdapterAlumni(listAlumni, this@MainActivity)

        url = "http://$ip/folder_kerja/tampil.php"
        sr = StringRequest(Request.Method.GET, url, {
            try {
                val obj = JSONObject(it)
                val array = obj.getJSONArray("data")
                for(i in 0 until array.length()) {
                    val ob = array.getJSONObject(i)
                    with(ob) {
                        listAlumni.add(
                            Alumni(
                            getString("nim"),
                            getString("nm_alumni"),
                            getString("prodi"),
                            getString("tmpt_lahir"),
                            getString("tgl_lahir"),
                            getString("alamat"),
                            getString("no_hp"),
                            getInt("thn_lulus")

                        )
                        )
                    }
                }
                rvAlumni.adapter = adapter
            } catch(_: JSONException) {
                Toast.makeText(this@MainActivity, "Tidak ada data...", Toast.LENGTH_LONG).show()
            }
        }, null)
        rq = Volley.newRequestQueue(this@MainActivity)
        rq.add(sr)
    }
}

and this koneksi.php

<!doctype html>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
</head>
<body>

</body>
</html>

I've no idea what should I change, try to remove the url the result was same, changing the IP but theres no change