Initial commit: Android Tether API app

Exposes phone connection status via HTTP API for tethered devices. Features: - Auto-start/stop server when tethering is enabled/disabled - REST API with /status and /health endpoints - Connection type, signal strength, carrier, battery info - Foreground service with persistent notification Stack: Kotlin 2.3, AGP 8.13, Gradle 8.13, compileSdk 36
2025-12-18 21:08:56 +01:00
commit 017172f48a
27 changed files with 1809 additions and 0 deletions
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
+    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_CONNECTED_DEVICE" />
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.TetherAPI"
+        tools:targetApi="34">
+
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:theme="@style/Theme.TetherAPI">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <service
+            android:name=".service.TetherApiService"
+            android:exported="false"
+            android:foregroundServiceType="connectedDevice" />
+
+        <receiver
+            android:name=".receiver.TetherStateReceiver"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.net.conn.TETHER_STATE_CHANGED" />
+            </intent-filter>
+        </receiver>
+
+    </application>
+
+</manifest>
--- a/app/src/main/java/dev/itsh/tetherapi/MainActivity.kt
+++ b/app/src/main/java/dev/itsh/tetherapi/MainActivity.kt
@@ -0,0 +1,210 @@
+package dev.itsh.tetherapi
+
+import android.Manifest
+import android.content.pm.PackageManager
+import android.graphics.drawable.GradientDrawable
+import android.os.Build
+import android.os.Bundle
+import android.os.Handler
+import android.os.Looper
+import android.widget.Toast
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.appcompat.app.AlertDialog
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
+import androidx.preference.PreferenceManager
+import com.google.gson.GsonBuilder
+import dev.itsh.tetherapi.databinding.ActivityMainBinding
+import dev.itsh.tetherapi.provider.StatusProvider
+import dev.itsh.tetherapi.receiver.TetherStateReceiver
+import dev.itsh.tetherapi.service.TetherApiService
+import java.net.NetworkInterface
+
+class MainActivity : AppCompatActivity() {
+
+    private lateinit var binding: ActivityMainBinding
+    private val handler = Handler(Looper.getMainLooper())
+    private val statusProvider by lazy { StatusProvider(this) }
+    private val gson = GsonBuilder().setPrettyPrinting().create()
+
+    private val requiredPermissions = buildList {
+        add(Manifest.permission.READ_PHONE_STATE)
+        add(Manifest.permission.ACCESS_FINE_LOCATION)
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            add(Manifest.permission.POST_NOTIFICATIONS)
+        }
+    }
+
+    private val permissionLauncher = registerForActivityResult(
+        ActivityResultContracts.RequestMultiplePermissions()
+    ) { permissions ->
+        val allGranted = permissions.all { it.value }
+        if (allGranted) {
+            updateUI()
+        } else {
+            showPermissionRationale()
+        }
+    }
+
+    private val updateRunnable = object : Runnable {
+        override fun run() {
+            updateUI()
+            handler.postDelayed(this, UPDATE_INTERVAL)
+        }
+    }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        binding = ActivityMainBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+
+        setupUI()
+        loadSettings()
+        checkPermissions()
+    }
+
+    override fun onResume() {
+        super.onResume()
+        handler.post(updateRunnable)
+    }
+
+    override fun onPause() {
+        super.onPause()
+        handler.removeCallbacks(updateRunnable)
+    }
+
+    private fun setupUI() {
+        binding.toggleButton.setOnClickListener {
+            if (TetherApiService.isRunning) {
+                TetherApiService.stop(this)
+            } else {
+                val port = binding.portInput.text.toString().toIntOrNull() ?: TetherApiService.DEFAULT_PORT
+                TetherApiService.start(this, port)
+            }
+            handler.postDelayed({ updateUI() }, 500)
+        }
+
+        binding.autoStartSwitch.setOnCheckedChangeListener { _, _ ->
+            saveSettings()
+        }
+
+        binding.portInput.setOnFocusChangeListener { _, hasFocus ->
+            if (!hasFocus) {
+                saveSettings()
+            }
+        }
+    }
+
+    private fun loadSettings() {
+        val prefs = PreferenceManager.getDefaultSharedPreferences(this)
+        binding.autoStartSwitch.isChecked = prefs.getBoolean(TetherStateReceiver.PREF_AUTO_START, true)
+        binding.portInput.setText(prefs.getInt(TetherStateReceiver.PREF_PORT, TetherApiService.DEFAULT_PORT).toString())
+    }
+
+    private fun saveSettings() {
+        val prefs = PreferenceManager.getDefaultSharedPreferences(this)
+        val port = binding.portInput.text.toString().toIntOrNull() ?: TetherApiService.DEFAULT_PORT
+        prefs.edit()
+            .putBoolean(TetherStateReceiver.PREF_AUTO_START, binding.autoStartSwitch.isChecked)
+            .putInt(TetherStateReceiver.PREF_PORT, port)
+            .apply()
+    }
+
+    private fun checkPermissions() {
+        val missingPermissions = requiredPermissions.filter {
+            ContextCompat.checkSelfPermission(this, it) != PackageManager.PERMISSION_GRANTED
+        }
+
+        if (missingPermissions.isNotEmpty()) {
+            permissionLauncher.launch(missingPermissions.toTypedArray())
+        }
+    }
+
+    private fun showPermissionRationale() {
+        AlertDialog.Builder(this)
+            .setTitle("Permissions Required")
+            .setMessage(
+                "This app needs the following permissions:\n\n" +
+                "• Phone State: To read network connection type and carrier\n" +
+                "• Location: Required by Android to access cell signal info\n" +
+                "• Notifications: To show service status"
+            )
+            .setPositiveButton("Grant") { _, _ ->
+                permissionLauncher.launch(requiredPermissions.toTypedArray())
+            }
+            .setNegativeButton("Cancel", null)
+            .show()
+    }
+
+    private fun updateUI() {
+        val isRunning = TetherApiService.isRunning
+        val port = TetherApiService.currentPort ?: binding.portInput.text.toString().toIntOrNull() ?: TetherApiService.DEFAULT_PORT
+
+        binding.statusText.text = if (isRunning) {
+            getString(R.string.status_running)
+        } else {
+            getString(R.string.status_stopped)
+        }
+
+        val statusColor = if (isRunning) {
+            ContextCompat.getColor(this, R.color.status_running)
+        } else {
+            ContextCompat.getColor(this, R.color.status_stopped)
+        }
+        (binding.statusIndicator.background as? GradientDrawable)?.setColor(statusColor)
+
+        binding.toggleButton.text = if (isRunning) {
+            getString(R.string.btn_stop)
+        } else {
+            getString(R.string.btn_start)
+        }
+
+        val gatewayIp = getGatewayIp()
+        binding.endpointText.text = if (gatewayIp != null) {
+            "http://$gatewayIp:$port/status"
+        } else {
+            "http://[phone-ip]:$port/status"
+        }
+
+        updateStatusPreview()
+    }
+
+    private fun updateStatusPreview() {
+        try {
+            val status = statusProvider.getStatus()
+            binding.previewText.text = gson.toJson(status)
+        } catch (e: Exception) {
+            binding.previewText.text = "Error: ${e.message}"
+        }
+    }
+
+    private fun getGatewayIp(): String? {
+        try {
+            val interfaces = NetworkInterface.getNetworkInterfaces()
+            while (interfaces.hasMoreElements()) {
+                val networkInterface = interfaces.nextElement()
+                val name = networkInterface.name.lowercase()
+
+                if (name.startsWith("rndis") || name.startsWith("usb") ||
+                    name.startsWith("wlan") || name.startsWith("ap") ||
+                    name.startsWith("swlan")) {
+
+                    val addresses = networkInterface.inetAddresses
+                    while (addresses.hasMoreElements()) {
+                        val address = addresses.nextElement()
+                        if (!address.isLoopbackAddress && address.hostAddress?.contains(".") == true) {
+                            return address.hostAddress
+                        }
+                    }
+                }
+            }
+        } catch (e: Exception) {
+            // Ignore
+        }
+        return null
+    }
+
+    companion object {
+        private const val UPDATE_INTERVAL = 2000L
+    }
+}
--- a/app/src/main/java/dev/itsh/tetherapi/api/ApiServer.kt
+++ b/app/src/main/java/dev/itsh/tetherapi/api/ApiServer.kt
@@ -0,0 +1,88 @@
+package dev.itsh.tetherapi.api
+
+import android.content.Context
+import com.google.gson.Gson
+import com.google.gson.GsonBuilder
+import dev.itsh.tetherapi.provider.StatusProvider
+import fi.iki.elonen.NanoHTTPD
+
+class ApiServer(
+    private val context: Context,
+    port: Int
+) : NanoHTTPD("0.0.0.0", port) {
+
+    private val statusProvider = StatusProvider(context)
+    private val gson: Gson = GsonBuilder()
+        .setPrettyPrinting()
+        .create()
+
+    override fun serve(session: IHTTPSession): Response {
+        val uri = session.uri
+        val method = session.method
+
+        if (method != Method.GET) {
+            return newFixedLengthResponse(
+                Response.Status.METHOD_NOT_ALLOWED,
+                MIME_JSON,
+                """{"error": "Method not allowed"}"""
+            ).apply {
+                addHeader("Access-Control-Allow-Origin", "*")
+            }
+        }
+
+        return when (uri) {
+            "/status" -> handleStatus()
+            "/health" -> handleHealth()
+            "/" -> handleRoot()
+            else -> handleNotFound()
+        }
+    }
+
+    private fun handleStatus(): Response {
+        return try {
+            val status = statusProvider.getStatus()
+            val json = gson.toJson(status)
+            jsonResponse(Response.Status.OK, json)
+        } catch (e: Exception) {
+            jsonResponse(
+                Response.Status.INTERNAL_ERROR,
+                """{"error": "${e.message ?: "Unknown error"}"}"""
+            )
+        }
+    }
+
+    private fun handleHealth(): Response {
+        return jsonResponse(Response.Status.OK, """{"status": "ok"}""")
+    }
+
+    private fun handleRoot(): Response {
+        val info = mapOf(
+            "name" to "Tether API",
+            "version" to "1.0.0",
+            "endpoints" to listOf(
+                mapOf("path" to "/status", "method" to "GET", "description" to "Get phone status"),
+                mapOf("path" to "/health", "method" to "GET", "description" to "Health check")
+            )
+        )
+        return jsonResponse(Response.Status.OK, gson.toJson(info))
+    }
+
+    private fun handleNotFound(): Response {
+        return jsonResponse(
+            Response.Status.NOT_FOUND,
+            """{"error": "Not found"}"""
+        )
+    }
+
+    private fun jsonResponse(status: Response.Status, json: String): Response {
+        return newFixedLengthResponse(status, MIME_JSON, json).apply {
+            addHeader("Access-Control-Allow-Origin", "*")
+            addHeader("Access-Control-Allow-Methods", "GET")
+            addHeader("Cache-Control", "no-cache")
+        }
+    }
+
+    companion object {
+        private const val MIME_JSON = "application/json"
+    }
+}
--- a/app/src/main/java/dev/itsh/tetherapi/data/PhoneStatus.kt
+++ b/app/src/main/java/dev/itsh/tetherapi/data/PhoneStatus.kt
@@ -0,0 +1,33 @@
+package dev.itsh.tetherapi.data
+
+import com.google.gson.annotations.SerializedName
+
+data class PhoneStatus(
+    val connection: ConnectionInfo,
+    val battery: BatteryInfo,
+    val network: NetworkInfo,
+    val timestamp: Long
+)
+
+data class ConnectionInfo(
+    val type: String,
+    @SerializedName("signal_dbm")
+    val signalDbm: Int,
+    @SerializedName("signal_bars")
+    val signalBars: Int,
+    val carrier: String,
+    val operator: String,
+    val roaming: Boolean
+)
+
+data class BatteryInfo(
+    val level: Int,
+    val charging: Boolean
+)
+
+data class NetworkInfo(
+    @SerializedName("wifi_ssid")
+    val wifiSsid: String?,
+    @SerializedName("ip_addresses")
+    val ipAddresses: List<String>
+)
--- a/app/src/main/java/dev/itsh/tetherapi/provider/StatusProvider.kt
+++ b/app/src/main/java/dev/itsh/tetherapi/provider/StatusProvider.kt
@@ -0,0 +1,255 @@
+package dev.itsh.tetherapi.provider
+
+import android.Manifest
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import android.content.pm.PackageManager
+import android.net.ConnectivityManager
+import android.net.NetworkCapabilities
+import android.net.wifi.WifiManager
+import android.os.BatteryManager
+import android.os.Build
+import android.telephony.CellInfo
+import android.telephony.CellInfoLte
+import android.telephony.CellInfoNr
+import android.telephony.CellInfoGsm
+import android.telephony.CellInfoWcdma
+import android.telephony.CellInfoCdma
+import android.telephony.TelephonyManager
+import androidx.core.content.ContextCompat
+import dev.itsh.tetherapi.data.BatteryInfo
+import dev.itsh.tetherapi.data.ConnectionInfo
+import dev.itsh.tetherapi.data.NetworkInfo
+import dev.itsh.tetherapi.data.PhoneStatus
+import java.net.NetworkInterface
+
+class StatusProvider(private val context: Context) {
+
+    private val telephonyManager: TelephonyManager by lazy {
+        context.getSystemService(Context.TELEPHONY_SERVICE) as TelephonyManager
+    }
+
+    private val connectivityManager: ConnectivityManager by lazy {
+        context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+    }
+
+    private val wifiManager: WifiManager by lazy {
+        context.applicationContext.getSystemService(Context.WIFI_SERVICE) as WifiManager
+    }
+
+    fun getStatus(): PhoneStatus {
+        return PhoneStatus(
+            connection = getConnectionInfo(),
+            battery = getBatteryInfo(),
+            network = getNetworkInfo(),
+            timestamp = System.currentTimeMillis() / 1000
+        )
+    }
+
+    private fun getConnectionInfo(): ConnectionInfo {
+        val hasPhonePermission = ContextCompat.checkSelfPermission(
+            context, Manifest.permission.READ_PHONE_STATE
+        ) == PackageManager.PERMISSION_GRANTED
+
+        val hasLocationPermission = ContextCompat.checkSelfPermission(
+            context, Manifest.permission.ACCESS_FINE_LOCATION
+        ) == PackageManager.PERMISSION_GRANTED
+
+        val connectionType = getConnectionType()
+        val (signalDbm, signalBars) = if (hasLocationPermission) {
+            getSignalStrength()
+        } else {
+            Pair(-999, 0)
+        }
+
+        val carrier = if (hasPhonePermission) {
+            telephonyManager.networkOperatorName ?: "Unknown"
+        } else {
+            "Unknown"
+        }
+
+        val operator = telephonyManager.networkOperator ?: ""
+
+        val isRoaming = try {
+            telephonyManager.isNetworkRoaming
+        } catch (e: Exception) {
+            false
+        }
+
+        return ConnectionInfo(
+            type = connectionType,
+            signalDbm = signalDbm,
+            signalBars = signalBars,
+            carrier = carrier,
+            operator = operator,
+            roaming = isRoaming
+        )
+    }
+
+    private fun getConnectionType(): String {
+        val network = connectivityManager.activeNetwork ?: return "NONE"
+        val capabilities = connectivityManager.getNetworkCapabilities(network) ?: return "NONE"
+
+        return when {
+            capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> "WIFI"
+            capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> getCellularType()
+            capabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> "ETHERNET"
+            else -> "UNKNOWN"
+        }
+    }
+
+    private fun getCellularType(): String {
+        val hasPermission = ContextCompat.checkSelfPermission(
+            context, Manifest.permission.READ_PHONE_STATE
+        ) == PackageManager.PERMISSION_GRANTED
+
+        if (!hasPermission) return "CELLULAR"
+
+        return when (telephonyManager.dataNetworkType) {
+            TelephonyManager.NETWORK_TYPE_NR -> "5G"
+            TelephonyManager.NETWORK_TYPE_LTE -> "LTE"
+            TelephonyManager.NETWORK_TYPE_HSPAP,
+            TelephonyManager.NETWORK_TYPE_HSPA,
+            TelephonyManager.NETWORK_TYPE_HSDPA,
+            TelephonyManager.NETWORK_TYPE_HSUPA -> "HSPA"
+            TelephonyManager.NETWORK_TYPE_UMTS,
+            TelephonyManager.NETWORK_TYPE_EVDO_0,
+            TelephonyManager.NETWORK_TYPE_EVDO_A,
+            TelephonyManager.NETWORK_TYPE_EVDO_B -> "3G"
+            TelephonyManager.NETWORK_TYPE_EDGE,
+            TelephonyManager.NETWORK_TYPE_GPRS,
+            TelephonyManager.NETWORK_TYPE_CDMA,
+            TelephonyManager.NETWORK_TYPE_1xRTT -> "2G"
+            TelephonyManager.NETWORK_TYPE_UNKNOWN -> "CELLULAR"
+            else -> "CELLULAR"
+        }
+    }
+
+    @Suppress("DEPRECATION")
+    private fun getSignalStrength(): Pair<Int, Int> {
+        val hasLocationPermission = ContextCompat.checkSelfPermission(
+            context, Manifest.permission.ACCESS_FINE_LOCATION
+        ) == PackageManager.PERMISSION_GRANTED
+
+        if (!hasLocationPermission) {
+            return Pair(-999, 0)
+        }
+
+        try {
+            val cellInfoList: List<CellInfo>? = telephonyManager.allCellInfo
+            if (cellInfoList.isNullOrEmpty()) {
+                return Pair(-999, 0)
+            }
+
+            for (cellInfo in cellInfoList) {
+                if (!cellInfo.isRegistered) continue
+
+                val dbm = when (cellInfo) {
+                    is CellInfoLte -> cellInfo.cellSignalStrength.dbm
+                    is CellInfoNr -> if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+                        cellInfo.cellSignalStrength.dbm
+                    } else -999
+                    is CellInfoGsm -> cellInfo.cellSignalStrength.dbm
+                    is CellInfoWcdma -> cellInfo.cellSignalStrength.dbm
+                    is CellInfoCdma -> cellInfo.cellSignalStrength.dbm
+                    else -> continue
+                }
+
+                val level = when (cellInfo) {
+                    is CellInfoLte -> cellInfo.cellSignalStrength.level
+                    is CellInfoNr -> if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+                        cellInfo.cellSignalStrength.level
+                    } else 0
+                    is CellInfoGsm -> cellInfo.cellSignalStrength.level
+                    is CellInfoWcdma -> cellInfo.cellSignalStrength.level
+                    is CellInfoCdma -> cellInfo.cellSignalStrength.level
+                    else -> continue
+                }
+
+                return Pair(dbm, level)
+            }
+        } catch (e: SecurityException) {
+            return Pair(-999, 0)
+        } catch (e: Exception) {
+            return Pair(-999, 0)
+        }
+
+        return Pair(-999, 0)
+    }
+
+    private fun getBatteryInfo(): BatteryInfo {
+        val batteryStatus: Intent? = IntentFilter(Intent.ACTION_BATTERY_CHANGED).let { filter ->
+            context.registerReceiver(null, filter)
+        }
+
+        val level = batteryStatus?.let { intent ->
+            val level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1)
+            val scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1)
+            if (level >= 0 && scale > 0) {
+                (level * 100 / scale)
+            } else {
+                -1
+            }
+        } ?: -1
+
+        val isCharging = batteryStatus?.let { intent ->
+            val status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1)
+            status == BatteryManager.BATTERY_STATUS_CHARGING ||
+                    status == BatteryManager.BATTERY_STATUS_FULL
+        } ?: false
+
+        return BatteryInfo(
+            level = level,
+            charging = isCharging
+        )
+    }
+
+    @Suppress("DEPRECATION")
+    private fun getNetworkInfo(): NetworkInfo {
+        val wifiSsid = try {
+            val network = connectivityManager.activeNetwork
+            val capabilities = connectivityManager.getNetworkCapabilities(network)
+            if (capabilities?.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) == true) {
+                val wifiInfo = wifiManager.connectionInfo
+                wifiInfo?.ssid?.replace("\"", "")?.takeIf { it != "<unknown ssid>" }
+            } else {
+                null
+            }
+        } catch (e: Exception) {
+            null
+        }
+
+        val ipAddresses = getIpAddresses()
+
+        return NetworkInfo(
+            wifiSsid = wifiSsid,
+            ipAddresses = ipAddresses
+        )
+    }
+
+    private fun getIpAddresses(): List<String> {
+        val addresses = mutableListOf<String>()
+        try {
+            val interfaces = NetworkInterface.getNetworkInterfaces()
+            while (interfaces.hasMoreElements()) {
+                val networkInterface = interfaces.nextElement()
+                if (networkInterface.isLoopback || !networkInterface.isUp) continue
+
+                val inetAddresses = networkInterface.inetAddresses
+                while (inetAddresses.hasMoreElements()) {
+                    val address = inetAddresses.nextElement()
+                    if (!address.isLoopbackAddress && !address.hostAddress.isNullOrEmpty()) {
+                        val hostAddress = address.hostAddress!!
+                        if (!hostAddress.contains(":")) {
+                            addresses.add(hostAddress)
+                        }
+                    }
+                }
+            }
+        } catch (e: Exception) {
+            // Ignore
+        }
+        return addresses
+    }
+}
--- a/app/src/main/java/dev/itsh/tetherapi/receiver/TetherStateReceiver.kt
+++ b/app/src/main/java/dev/itsh/tetherapi/receiver/TetherStateReceiver.kt
@@ -0,0 +1,61 @@
+package dev.itsh.tetherapi.receiver
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.net.ConnectivityManager
+import android.os.Build
+import androidx.preference.PreferenceManager
+import dev.itsh.tetherapi.service.TetherApiService
+
+class TetherStateReceiver : BroadcastReceiver() {
+
+    override fun onReceive(context: Context, intent: Intent) {
+        if (intent.action != ACTION_TETHER_STATE_CHANGED) return
+
+        val prefs = PreferenceManager.getDefaultSharedPreferences(context)
+        val autoStartEnabled = prefs.getBoolean(PREF_AUTO_START, true)
+
+        if (!autoStartEnabled) return
+
+        val isTethering = isTetherActive(context, intent)
+        val port = prefs.getInt(PREF_PORT, TetherApiService.DEFAULT_PORT)
+
+        if (isTethering && !TetherApiService.isRunning) {
+            TetherApiService.start(context, port)
+        } else if (!isTethering && TetherApiService.isRunning) {
+            TetherApiService.stop(context)
+        }
+    }
+
+    @Suppress("DEPRECATION")
+    private fun isTetherActive(context: Context, intent: Intent): Boolean {
+        val extras = intent.extras ?: return false
+
+        val activeList = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            extras.getStringArrayList("activeArray")
+        } else {
+            @Suppress("UNCHECKED_CAST")
+            extras.get("activeArray") as? ArrayList<String>
+        }
+
+        if (!activeList.isNullOrEmpty()) {
+            return true
+        }
+
+        return try {
+            val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+            val method = cm.javaClass.getDeclaredMethod("getTetheredIfaces")
+            val tetheredIfaces = method.invoke(cm) as? Array<*>
+            tetheredIfaces != null && tetheredIfaces.isNotEmpty()
+        } catch (e: Exception) {
+            false
+        }
+    }
+
+    companion object {
+        const val ACTION_TETHER_STATE_CHANGED = "android.net.conn.TETHER_STATE_CHANGED"
+        const val PREF_AUTO_START = "auto_start_on_tether"
+        const val PREF_PORT = "api_port"
+    }
+}
--- a/app/src/main/java/dev/itsh/tetherapi/service/TetherApiService.kt
+++ b/app/src/main/java/dev/itsh/tetherapi/service/TetherApiService.kt
@@ -0,0 +1,163 @@
+package dev.itsh.tetherapi.service
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.app.Service
+import android.content.Context
+import android.content.Intent
+import android.os.Binder
+import android.os.Build
+import android.os.IBinder
+import androidx.core.app.NotificationCompat
+import dev.itsh.tetherapi.MainActivity
+import dev.itsh.tetherapi.R
+import dev.itsh.tetherapi.api.ApiServer
+
+class TetherApiService : Service() {
+
+    private var apiServer: ApiServer? = null
+    private val binder = LocalBinder()
+
+    inner class LocalBinder : Binder() {
+        fun getService(): TetherApiService = this@TetherApiService
+    }
+
+    override fun onBind(intent: Intent?): IBinder = binder
+
+    override fun onCreate() {
+        super.onCreate()
+        createNotificationChannel()
+    }
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        val port = intent?.getIntExtra(EXTRA_PORT, DEFAULT_PORT) ?: DEFAULT_PORT
+
+        when (intent?.action) {
+            ACTION_START -> startServer(port)
+            ACTION_STOP -> stopServer()
+        }
+
+        return START_STICKY
+    }
+
+    private fun startServer(port: Int) {
+        if (apiServer?.isAlive == true) {
+            return
+        }
+
+        try {
+            apiServer = ApiServer(this, port).apply {
+                start()
+            }
+
+            val notification = createNotification(port)
+            startForeground(NOTIFICATION_ID, notification)
+
+            isRunning = true
+            currentPort = port
+        } catch (e: Exception) {
+            stopSelf()
+        }
+    }
+
+    private fun stopServer() {
+        apiServer?.stop()
+        apiServer = null
+        isRunning = false
+        currentPort = null
+        stopForeground(STOP_FOREGROUND_REMOVE)
+        stopSelf()
+    }
+
+    override fun onDestroy() {
+        stopServer()
+        super.onDestroy()
+    }
+
+    private fun createNotificationChannel() {
+        val channel = NotificationChannel(
+            CHANNEL_ID,
+            getString(R.string.service_notification_channel),
+            NotificationManager.IMPORTANCE_LOW
+        ).apply {
+            description = "Shows when Tether API server is running"
+            setShowBadge(false)
+        }
+
+        val notificationManager = getSystemService(NotificationManager::class.java)
+        notificationManager.createNotificationChannel(channel)
+    }
+
+    private fun createNotification(port: Int): Notification {
+        val intent = Intent(this, MainActivity::class.java).apply {
+            flags = Intent.FLAG_ACTIVITY_SINGLE_TOP
+        }
+
+        val pendingIntent = PendingIntent.getActivity(
+            this,
+            0,
+            intent,
+            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT
+        )
+
+        val stopIntent = Intent(this, TetherApiService::class.java).apply {
+            action = ACTION_STOP
+        }
+
+        val stopPendingIntent = PendingIntent.getService(
+            this,
+            1,
+            stopIntent,
+            PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT
+        )
+
+        return NotificationCompat.Builder(this, CHANNEL_ID)
+            .setContentTitle(getString(R.string.service_notification_title))
+            .setContentText(getString(R.string.service_notification_text, port))
+            .setSmallIcon(R.drawable.ic_notification)
+            .setContentIntent(pendingIntent)
+            .addAction(0, "Stop", stopPendingIntent)
+            .setOngoing(true)
+            .setPriority(NotificationCompat.PRIORITY_LOW)
+            .setCategory(NotificationCompat.CATEGORY_SERVICE)
+            .build()
+    }
+
+    companion object {
+        const val ACTION_START = "dev.itsh.tetherapi.action.START"
+        const val ACTION_STOP = "dev.itsh.tetherapi.action.STOP"
+        const val EXTRA_PORT = "dev.itsh.tetherapi.extra.PORT"
+        const val DEFAULT_PORT = 8765
+
+        private const val CHANNEL_ID = "tether_api_service"
+        private const val NOTIFICATION_ID = 1
+
+        var isRunning = false
+            private set
+
+        var currentPort: Int? = null
+            private set
+
+        fun start(context: Context, port: Int = DEFAULT_PORT) {
+            val intent = Intent(context, TetherApiService::class.java).apply {
+                action = ACTION_START
+                putExtra(EXTRA_PORT, port)
+            }
+
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                context.startForegroundService(intent)
+            } else {
+                context.startService(intent)
+            }
+        }
+
+        fun stop(context: Context) {
+            val intent = Intent(context, TetherApiService::class.java).apply {
+                action = ACTION_STOP
+            }
+            context.startService(intent)
+        }
+    }
+}
--- a/app/src/main/res/drawable/ic_launcher_foreground.xml
+++ b/app/src/main/res/drawable/ic_launcher_foreground.xml
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <!-- Signal bars icon centered in adaptive icon safe zone -->
+    <group
+        android:translateX="27"
+        android:translateY="27">
+        <!-- Bar 1 (shortest) -->
+        <path
+            android:fillColor="#FFFFFF"
+            android:pathData="M4,44 L12,44 L12,54 L4,54 Z" />
+        <!-- Bar 2 -->
+        <path
+            android:fillColor="#FFFFFF"
+            android:pathData="M16,34 L24,34 L24,54 L16,54 Z" />
+        <!-- Bar 3 -->
+        <path
+            android:fillColor="#FFFFFF"
+            android:pathData="M28,24 L36,24 L36,54 L28,54 Z" />
+        <!-- Bar 4 (tallest) -->
+        <path
+            android:fillColor="#FFFFFF"
+            android:pathData="M40,14 L48,14 L48,54 L40,54 Z" />
+        <!-- API text -->
+        <path
+            android:fillColor="#FFFFFF"
+            android:pathData="M4,4 L10,4 L14,12 L18,4 L24,4 L24,6 L20,6 L16,14 L12,6 L8,6 L8,4 Z" />
+    </group>
+</vector>
--- a/app/src/main/res/drawable/ic_notification.xml
+++ b/app/src/main/res/drawable/ic_notification.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <!-- Signal bars -->
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M2,20 L4,20 L4,16 L2,16 Z" />
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M6,20 L8,20 L8,12 L6,12 Z" />
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M10,20 L12,20 L12,8 L10,8 Z" />
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M14,20 L16,20 L16,4 L14,4 Z" />
+    <!-- API indicator -->
+    <path
+        android:fillColor="#FFFFFF"
+        android:pathData="M18,8 L22,8 L22,20 L20,20 L20,15 L18,15 L18,20 L18,8 M20,10 L20,13 L20,10 Z" />
+</vector>
--- a/app/src/main/res/drawable/status_indicator.xml
+++ b/app/src/main/res/drawable/status_indicator.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="oval">
+    <solid android:color="@color/status_stopped" />
+</shape>
--- a/app/src/main/res/layout/activity_main.xml
+++ b/app/src/main/res/layout/activity_main.xml
@@ -0,0 +1,177 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:padding="16dp"
+    tools:context=".MainActivity">
+
+    <TextView
+        android:id="@+id/titleText"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/app_name"
+        android:textSize="28sp"
+        android:textStyle="bold"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <com.google.android.material.card.MaterialCardView
+        android:id="@+id/statusCard"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="24dp"
+        app:cardCornerRadius="12dp"
+        app:cardElevation="4dp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/titleText">
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="vertical"
+            android:padding="16dp">
+
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:gravity="center_vertical"
+                android:orientation="horizontal">
+
+                <View
+                    android:id="@+id/statusIndicator"
+                    android:layout_width="12dp"
+                    android:layout_height="12dp"
+                    android:background="@drawable/status_indicator" />
+
+                <TextView
+                    android:id="@+id/statusText"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:layout_marginStart="8dp"
+                    android:text="@string/status_stopped"
+                    android:textSize="18sp"
+                    android:textStyle="bold" />
+            </LinearLayout>
+
+            <TextView
+                android:id="@+id/endpointLabel"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="12dp"
+                android:text="@string/label_endpoint"
+                android:textColor="?android:textColorSecondary"
+                android:textSize="12sp" />
+
+            <TextView
+                android:id="@+id/endpointText"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:fontFamily="monospace"
+                android:textIsSelectable="true"
+                android:textSize="14sp"
+                tools:text="http://192.168.42.1:8765/status" />
+
+        </LinearLayout>
+    </com.google.android.material.card.MaterialCardView>
+
+    <com.google.android.material.button.MaterialButton
+        android:id="@+id/toggleButton"
+        android:layout_width="match_parent"
+        android:layout_height="56dp"
+        android:layout_marginTop="24dp"
+        android:text="@string/btn_start"
+        android:textSize="16sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/statusCard" />
+
+    <com.google.android.material.card.MaterialCardView
+        android:id="@+id/settingsCard"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="24dp"
+        app:cardCornerRadius="12dp"
+        app:cardElevation="4dp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/toggleButton">
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="vertical"
+            android:padding="16dp">
+
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:gravity="center_vertical"
+                android:orientation="horizontal">
+
+                <TextView
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:text="@string/label_port"
+                    android:textSize="16sp" />
+
+                <com.google.android.material.textfield.TextInputEditText
+                    android:id="@+id/portInput"
+                    android:layout_width="100dp"
+                    android:layout_height="wrap_content"
+                    android:gravity="center"
+                    android:inputType="number"
+                    android:maxLength="5"
+                    android:text="8765" />
+
+            </LinearLayout>
+
+            <com.google.android.material.switchmaterial.SwitchMaterial
+                android:id="@+id/autoStartSwitch"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:checked="true"
+                android:text="@string/label_auto_start" />
+
+        </LinearLayout>
+    </com.google.android.material.card.MaterialCardView>
+
+    <TextView
+        android:id="@+id/previewTitle"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="24dp"
+        android:text="Current Status Preview"
+        android:textSize="14sp"
+        android:textStyle="bold"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/settingsCard" />
+
+    <HorizontalScrollView
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_marginTop="8dp"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/previewTitle">
+
+        <TextView
+            android:id="@+id/previewText"
+            android:layout_width="wrap_content"
+            android:layout_height="match_parent"
+            android:background="#F5F5F5"
+            android:fontFamily="monospace"
+            android:padding="12dp"
+            android:textIsSelectable="true"
+            android:textSize="11sp"
+            tools:text='{"connection": {...}}' />
+
+    </HorizontalScrollView>
+
+</androidx.constraintlayout.widget.ConstraintLayout>
--- a/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml
+++ b/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/primary"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>
--- a/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml
+++ b/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/primary"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>
--- a/app/src/main/res/values/colors.xml
+++ b/app/src/main/res/values/colors.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="primary">#1976D2</color>
+    <color name="primary_variant">#1565C0</color>
+    <color name="secondary">#26A69A</color>
+    <color name="background">#FAFAFA</color>
+    <color name="surface">#FFFFFF</color>
+    <color name="error">#B00020</color>
+    <color name="on_primary">#FFFFFF</color>
+    <color name="on_secondary">#000000</color>
+    <color name="on_background">#000000</color>
+    <color name="on_surface">#000000</color>
+    <color name="on_error">#FFFFFF</color>
+    <color name="status_running">#4CAF50</color>
+    <color name="status_stopped">#9E9E9E</color>
+</resources>
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">Tether API</string>
+    <string name="service_notification_channel">Tether API Service</string>
+    <string name="service_notification_title">Tether API Running</string>
+    <string name="service_notification_text">API server active on port %d</string>
+    <string name="status_running">Running</string>
+    <string name="status_stopped">Stopped</string>
+    <string name="btn_start">Start Server</string>
+    <string name="btn_stop">Stop Server</string>
+    <string name="label_endpoint">API Endpoint</string>
+    <string name="label_port">Port</string>
+    <string name="label_auto_start">Auto-start on tether</string>
+    <string name="permission_rationale_location">Location permission is required to access cell signal information on Android 10+</string>
+    <string name="permission_rationale_phone">Phone state permission is required to read network connection information</string>
+    <string name="permission_rationale_notification">Notification permission allows showing the service status</string>
+</resources>
--- a/app/src/main/res/values/themes.xml
+++ b/app/src/main/res/values/themes.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <style name="Theme.TetherAPI" parent="Theme.Material3.Light.NoActionBar">
+        <item name="colorPrimary">@color/primary</item>
+        <item name="colorPrimaryVariant">@color/primary_variant</item>
+        <item name="colorSecondary">@color/secondary</item>
+        <item name="android:colorBackground">@color/background</item>
+        <item name="colorSurface">@color/surface</item>
+        <item name="colorError">@color/error</item>
+        <item name="colorOnPrimary">@color/on_primary</item>
+        <item name="colorOnSecondary">@color/on_secondary</item>
+        <item name="colorOnBackground">@color/on_background</item>
+        <item name="colorOnSurface">@color/on_surface</item>
+        <item name="colorOnError">@color/on_error</item>
+    </style>
+</resources>