Add the Android app: Gradle build, Oboe audio, connection screen

android/ builds core and ts3j from the same sources as the desktop's
Maven build, so the app shares all of the client's logic:

- audio: Oboe streams behind AudioCapture/AudioPlayback, with a lock-free
  ring between the real-time callback and the blocking Java side, and
  libopus 1.5.2 built with the NDK behind OpusCodec. Speakers are mixed
  onto one stream. Capture uses the VoiceRecognition preset, leaving
  noise suppression and gain to the client's own processing.
- app: a plain connection screen to try the port out - connect,
  microphone, mute, deafen, channel chat and a log - until the real UI.

Targets Android 13 and up (minSdk 33) on arm64 and x86_64.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -10,6 +10,7 @@ out/
 
 # Packages
 *.jar
+!android/gradle/wrapper/gradle-wrapper.jar
 *.war
 *.zip
 *.tar.gz
@@ -35,3 +36,9 @@ release.properties
 
 # OS
 .DS_Store
+
+# Android / Gradle
+android/.gradle/
+android/.kotlin/
+android/**/.cxx/
+android/local.properties

android/app/build.gradle.kts

@@ -0,0 +1,55 @@
+plugins {
+    alias(libs.plugins.android.application)
+    alias(libs.plugins.kotlin.compose)
+}
+
+android {
+    namespace = "com.ts3client.android"
+    compileSdk = 37
+    ndkVersion = "30.0.16248370"
+
+    defaultConfig {
+        applicationId = "com.ts3client.android"
+        minSdk = 33
+        targetSdk = 36
+        versionCode = 1
+        versionName = "0.1.0"
+        ndk {
+            abiFilters += listOf("arm64-v8a", "x86_64")
+        }
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = true
+            proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
+        }
+    }
+
+    buildFeatures {
+        compose = true
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    packaging {
+        resources {
+            // BouncyCastle ships Java 9+ module metadata Android has no use for.
+            excludes += "META-INF/versions/9/OSGI-INF/MANIFEST.MF"
+        }
+    }
+}
+
+dependencies {
+    implementation(project(":audio"))
+
+    implementation(platform(libs.androidx.compose.bom))
+    implementation(libs.androidx.compose.ui)
+    implementation(libs.androidx.compose.material3)
+    implementation(libs.androidx.activity.compose)
+    implementation(libs.androidx.lifecycle.runtime.compose)
+    implementation(libs.androidx.lifecycle.viewmodel.compose)
+}

android/app/proguard-rules.pro

@@ -0,0 +1,10 @@
+# ts3j looks up SRV records through JNDI only where it exists; Android lacks it.
+-dontwarn javax.naming.**
+
+# Reached from native code by name.
+-keepclasseswithmembernames class com.ts3client.android.audio.** {
+    native <methods>;
+}
+
+# ts3j builds protocol handlers and packet bodies reflectively.
+-keep class com.github.manevolent.ts3j.** { *; }

android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+
+    <application
+        android:name=".Ts3Application"
+        android:label="@string/app_name"
+        android:theme="@android:style/Theme.Material.NoActionBar">
+
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:windowSoftInputMode="adjustResize">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>

android/app/src/main/java/com/ts3client/android/MainActivity.kt

@@ -0,0 +1,119 @@
+package com.ts3client.android
+
+import android.Manifest
+import android.content.pm.PackageManager
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.compose.setContent
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.safeDrawingPadding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.lazy.rememberLazyListState
+import androidx.compose.material3.Button
+import androidx.compose.material3.FilterChip
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.material3.darkColorScheme
+import androidx.compose.material3.lightColorScheme
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.unit.dp
+import androidx.core.content.ContextCompat
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.viewmodel.compose.viewModel
+
+class MainActivity : ComponentActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContent {
+            MaterialTheme(colorScheme = if (isSystemInDarkTheme()) darkColorScheme() else lightColorScheme()) {
+                Surface(Modifier.fillMaxSize()) {
+                    ConnectionScreen(viewModel())
+                }
+            }
+        }
+    }
+}
+
+/** A bare connection screen for trying the port out; the real UI replaces it. */
+@Composable
+private fun ConnectionScreen(vm: SessionViewModel) {
+    val state by vm.state.collectAsStateWithLifecycle()
+    var address by remember { mutableStateOf(vm.lastAddress) }
+    var nickname by remember { mutableStateOf(vm.nickname) }
+    var message by remember { mutableStateOf("") }
+
+    val context = LocalContext.current
+    val micPermission = rememberLauncherForActivityResult(ActivityResultContracts.RequestPermission()) { granted ->
+        if (granted) vm.setMicrophoneActive(true)
+    }
+
+    Column(
+        Modifier.safeDrawingPadding().padding(12.dp),
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Text("${state.title} — ${state.status}", style = MaterialTheme.typography.titleMedium)
+        if (state.connected) Text("${state.channels} channels, ${state.clients} clients")
+
+        OutlinedTextField(address, { address = it }, Modifier.fillMaxWidth(), label = { Text("Server") },
+            singleLine = true, enabled = !state.busy)
+        OutlinedTextField(nickname, { nickname = it }, Modifier.fillMaxWidth(), label = { Text("Nickname") },
+            singleLine = true, enabled = !state.busy)
+
+        Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+            if (state.busy) {
+                Button(onClick = vm::disconnect) { Text("Disconnect") }
+            } else {
+                Button(onClick = { vm.connect(address, nickname) }, enabled = address.isNotBlank()) { Text("Connect") }
+            }
+        }
+        Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+            FilterChip(state.micActive, onClick = {
+                if (state.micActive) {
+                    vm.setMicrophoneActive(false)
+                } else if (ContextCompat.checkSelfPermission(context, Manifest.permission.RECORD_AUDIO)
+                    == PackageManager.PERMISSION_GRANTED) {
+                    vm.setMicrophoneActive(true)
+                } else {
+                    micPermission.launch(Manifest.permission.RECORD_AUDIO)
+                }
+            }, label = { Text("Microphone") })
+            FilterChip(state.micMuted, onClick = { vm.setMicMuted(!state.micMuted) }, label = { Text("Mute") })
+            FilterChip(state.deafened, onClick = { vm.setDeafened(!state.deafened) }, label = { Text("Deafen") })
+        }
+
+        val listState = rememberLazyListState()
+        LaunchedEffect(state.log.size) {
+            if (state.log.isNotEmpty()) listState.animateScrollToItem(state.log.size - 1)
+        }
+        LazyColumn(Modifier.weight(1f).fillMaxWidth(), state = listState) {
+            items(state.log) { Text(it, style = MaterialTheme.typography.bodySmall) }
+        }
+
+        Row(verticalAlignment = androidx.compose.ui.Alignment.CenterVertically) {
+            OutlinedTextField(message, { message = it }, Modifier.weight(1f), label = { Text("Channel chat") },
+                singleLine = true, enabled = state.connected)
+            Button(onClick = { vm.sendChannelMessage(message); message = "" },
+                enabled = state.connected && message.isNotBlank(), modifier = Modifier.padding(start = 8.dp)) {
+                Text("Send")
+            }
+        }
+    }
+}

android/app/src/main/java/com/ts3client/android/SessionViewModel.kt

@@ -0,0 +1,123 @@
+package com.ts3client.android
+
+import android.app.Application
+import android.text.Html
+import androidx.lifecycle.AndroidViewModel
+import com.ts3client.android.audio.AndroidAudioBackend
+import com.ts3client.config.IdentityStore
+import com.ts3client.config.Settings
+import com.ts3client.contacts.ContactStore
+import com.ts3client.net.ConnectionListener.ChatScope
+import com.ts3client.session.ServerSession
+import com.ts3client.sound.SoundNotifier
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.update
+
+/** What the connection screen shows. */
+data class SessionState(
+    val title: String = "",
+    val status: String = "Not connected",
+    val connected: Boolean = false,
+    val busy: Boolean = false,
+    val micActive: Boolean = false,
+    val micMuted: Boolean = false,
+    val deafened: Boolean = false,
+    val channels: Int = 0,
+    val clients: Int = 0,
+    val log: List<String> = emptyList(),
+)
+
+/**
+ * Holds one [ServerSession] and mirrors what it reports into [state]. Session callbacks
+ * arrive on connection threads; [MutableStateFlow] takes updates from any of them.
+ */
+class SessionViewModel(app: Application) : AndroidViewModel(app) {
+
+    private val settings = Settings.load()
+    private val audio = AndroidAudioBackend(app)
+    private val sounds = SoundNotifier(settings).also { it.setPlayer(audio.createSoundPlayer(settings)) }
+    private val session = ServerSession(
+        settings, IdentityStore.load(settings), audio, sounds, ContactStore.load(), Listener()
+    )
+
+    private val _state = MutableStateFlow(SessionState(title = session.title()))
+    val state: StateFlow<SessionState> = _state
+
+    val nickname: String get() = settings.nickname
+    val lastAddress: String get() = settings.lastAddress
+
+    fun connect(address: String, nickname: String) {
+        val host = address.substringBefore(':').trim()
+        val port = address.substringAfter(':', "9987").trim().toIntOrNull() ?: 9987
+        settings.lastAddress = address
+        settings.nickname = nickname
+        settings.save()
+        session.connect(host, port, nickname, "", "", "", "")
+    }
+
+    fun disconnect() = session.disconnect()
+
+    /** Hands the microphone to the connection; needs RECORD_AUDIO granted. */
+    fun setMicrophoneActive(active: Boolean) {
+        session.setMicrophoneActive(active)
+        refresh()
+    }
+
+    fun setMicMuted(muted: Boolean) = session.setMicMuted(muted)
+
+    fun setDeafened(deafened: Boolean) = session.setDeafened(deafened)
+
+    fun sendChannelMessage(text: String) = session.sendChat(ChatScope.CHANNEL, 0, text)
+
+    override fun onCleared() {
+        Thread { session.shutdown() }.start()
+    }
+
+    private fun refresh() {
+        val model = session.connection().model
+        _state.update {
+            it.copy(
+                title = session.title(),
+                status = session.status(),
+                connected = session.isConnected(),
+                busy = session.isBusy(),
+                micActive = session.connection().isMicrophoneActive,
+                micMuted = session.isMicMuted(),
+                deafened = session.isDeafened(),
+                channels = model.buildTree().sumOf { countChannels(it) },
+                clients = model.allClients().size,
+            )
+        }
+    }
+
+    private fun countChannels(node: com.ts3client.net.ChannelNode): Int =
+        1 + node.children.sumOf { countChannels(it) }
+
+    private fun log(line: String) {
+        _state.update { it.copy(log = (it.log + line).takeLast(500)) }
+    }
+
+    private inner class Listener : ServerSession.Listener {
+        override fun onSessionChanged() = refresh()
+        override fun onSystemMessage(text: String) = log(text)
+        override fun onOwnChat(scope: ChatScope, peerClientId: Int, peerName: String, text: String) =
+            log("<you> $text")
+
+        override fun onStatus(status: String) {}
+        override fun onConnected() = refresh()
+        override fun onDisconnected(reason: String?) = refresh()
+        override fun onModelChanged() = refresh()
+        override fun onInfoUpdated() {}
+        override fun onIconsUpdated() {}
+        override fun onChat(scope: ChatScope, fromClientId: Int, fromUniqueId: String?, fromName: String, message: String) =
+            log("<$fromName> $message")
+
+        override fun onTalkStateChanged(clientId: Int, talking: Boolean) {}
+        override fun onError(message: String) {}
+        override fun onPoke(fromName: String, message: String) {}
+        override fun onServerLog(message: String) = log(plain(message))
+    }
+
+    private fun plain(html: String) = Html.fromHtml(html, Html.FROM_HTML_MODE_COMPACT).toString().trim()
+}

android/app/src/main/java/com/ts3client/android/Ts3Application.kt

@@ -0,0 +1,12 @@
+package com.ts3client.android
+
+import android.app.Application
+import com.ts3client.config.AppDirs
+
+class Ts3Application : Application() {
+    override fun onCreate() {
+        super.onCreate()
+        // Before any store loads: there is no home directory to find them in.
+        AppDirs.init(filesDir, filesDir.toPath().resolve("chats"))
+    }
+}

android/app/src/main/res/values/strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">TS3J</string>
+</resources>

android/audio/build.gradle.kts

@@ -0,0 +1,42 @@
+plugins {
+    alias(libs.plugins.android.library)
+}
+
+android {
+    namespace = "com.ts3client.android.audio"
+    compileSdk = 37
+    ndkVersion = "30.0.16248370"
+
+    defaultConfig {
+        minSdk = 33
+        ndk {
+            abiFilters += listOf("arm64-v8a", "x86_64")
+        }
+        externalNativeBuild {
+            cmake {
+                arguments += "-DANDROID_STL=c++_shared"
+            }
+        }
+    }
+
+    buildFeatures {
+        prefab = true
+    }
+
+    externalNativeBuild {
+        cmake {
+            path = file("src/main/cpp/CMakeLists.txt")
+            version = "4.1.2"
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+}
+
+dependencies {
+    api(project(":core"))
+    implementation(libs.oboe)
+}

android/audio/src/main/cpp/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.22)
+project(ts3audio LANGUAGES C CXX)
+
+set(CMAKE_CXX_STANDARD 20)
+
+find_package(oboe REQUIRED CONFIG)
+
+# libopus from its release tarball, built static into our one library.
+include(FetchContent)
+FetchContent_Declare(opus
+        URL https://github.com/xiph/opus/releases/download/v1.5.2/opus-1.5.2.tar.gz
+        URL_HASH SHA256=65c1d2f78b9f2fb20082c38cbe47c951ad5839345876e46941612ee87f9a7ce1)
+set(OPUS_BUILD_PROGRAMS OFF CACHE BOOL "" FORCE)
+set(OPUS_BUILD_TESTING OFF CACHE BOOL "" FORCE)
+set(OPUS_BUILD_SHARED_LIBRARY OFF CACHE BOOL "" FORCE)
+set(OPUS_INSTALL_PKG_CONFIG_MODULE OFF CACHE BOOL "" FORCE)
+set(OPUS_INSTALL_CMAKE_CONFIG_MODULE OFF CACHE BOOL "" FORCE)
+FetchContent_MakeAvailable(opus)
+
+add_library(ts3audio SHARED audio_line.cpp opus_jni.cpp)
+target_link_libraries(ts3audio PRIVATE oboe::oboe opus log)
+target_compile_options(ts3audio PRIVATE -Wall -Wextra)

android/audio/src/main/cpp/audio_line.cpp

@@ -0,0 +1,241 @@
+// An Oboe stream behind the blocking read/write interface of AudioCapture and AudioPlayback.
+//
+// The real-time callback never waits and never calls into Java: it only moves samples
+// between the device and a lock-free ring, which the Java side fills or drains at its own
+// pace, blocking while the ring is full (playback) or short (capture).
+
+#include <jni.h>
+#include <oboe/Oboe.h>
+#include <android/log.h>
+
+#include <algorithm>
+#include <atomic>
+#include <chrono>
+#include <cstring>
+#include <memory>
+#include <mutex>
+#include <thread>
+#include <vector>
+
+namespace {
+
+constexpr int32_t kSampleRate = 48000;
+constexpr int32_t kFrameSize = 960;  // 20 ms
+// Capture keeps some slack for a Java thread that is briefly late; playback keeps little,
+// since everything queued is latency.
+constexpr int32_t kCaptureFrames = 8;
+constexpr int32_t kPlaybackFrames = 3;
+constexpr auto kPollInterval = std::chrono::milliseconds(1);
+
+const char *kTag = "ts3audio";
+
+/** Single-producer, single-consumer ring of 16-bit samples. */
+class SampleRing {
+public:
+    explicit SampleRing(size_t capacity) : buffer_(capacity) {}
+
+    size_t available() const {
+        return head_.load(std::memory_order_acquire) - tail_.load(std::memory_order_acquire);
+    }
+
+    size_t space() const { return buffer_.size() - available(); }
+
+    /** Producer side: stores as much of {@code data} as fits. */
+    size_t write(const int16_t *data, size_t count) {
+        size_t head = head_.load(std::memory_order_relaxed);
+        size_t tail = tail_.load(std::memory_order_acquire);
+        size_t n = std::min(count, buffer_.size() - (head - tail));
+        for (size_t i = 0; i < n; i++) buffer_[(head + i) % buffer_.size()] = data[i];
+        head_.store(head + n, std::memory_order_release);
+        return n;
+    }
+
+    /** Consumer side: takes up to {@code count} samples. */
+    size_t read(int16_t *data, size_t count) {
+        size_t tail = tail_.load(std::memory_order_relaxed);
+        size_t head = head_.load(std::memory_order_acquire);
+        size_t n = std::min(count, head - tail);
+        for (size_t i = 0; i < n; i++) data[i] = buffer_[(tail + i) % buffer_.size()];
+        tail_.store(tail + n, std::memory_order_release);
+        return n;
+    }
+
+private:
+    std::vector<int16_t> buffer_;
+    std::atomic<size_t> head_{0};
+    std::atomic<size_t> tail_{0};
+};
+
+class AudioLine : public oboe::AudioStreamDataCallback, public oboe::AudioStreamErrorCallback {
+public:
+    AudioLine(bool input, int32_t deviceId, int32_t channels)
+            : input_(input), deviceId_(deviceId), channels_(channels),
+              ring_(static_cast<size_t>(kFrameSize) * channels * (input ? kCaptureFrames : kPlaybackFrames)) {}
+
+    int32_t channels() const { return channels_; }
+
+    oboe::Result open() {
+        oboe::AudioStreamBuilder builder;
+        builder.setDirection(input_ ? oboe::Direction::Input : oboe::Direction::Output)
+                ->setSharingMode(oboe::SharingMode::Shared)
+                ->setPerformanceMode(oboe::PerformanceMode::LowLatency)
+                ->setFormat(oboe::AudioFormat::I16)
+                ->setFormatConversionAllowed(true)
+                ->setChannelCount(channels_)
+                ->setChannelConversionAllowed(true)
+                ->setSampleRate(kSampleRate)
+                ->setSampleRateConversionQuality(oboe::SampleRateConversionQuality::Medium)
+                ->setDataCallback(this)
+                ->setErrorCallback(this);
+        if (deviceId_ > 0) builder.setDeviceId(deviceId_);
+        if (input_) {
+            // The platform's own voice processing stays off: the client runs TS3's.
+            builder.setInputPreset(oboe::InputPreset::VoiceRecognition);
+        } else {
+            builder.setUsage(oboe::Usage::Media)->setContentType(oboe::ContentType::Speech);
+        }
+        std::shared_ptr<oboe::AudioStream> stream;
+        oboe::Result result = builder.openStream(stream);
+        if (result != oboe::Result::OK) return result;
+        std::lock_guard<std::mutex> lock(mutex_);
+        if (closing_.load()) {  // closed while a reopen was under way
+            stream->close();
+            return oboe::Result::ErrorClosed;
+        }
+        stream_ = stream;
+        return result;
+    }
+
+    oboe::Result start() {
+        std::lock_guard<std::mutex> lock(mutex_);
+        return stream_ ? stream_->requestStart() : oboe::Result::ErrorClosed;
+    }
+
+    /** Blocks until {@code count} samples are captured; fewer only once closing. */
+    size_t read(int16_t *data, size_t count) {
+        size_t done = 0;
+        while (done < count && !closing_.load()) {
+            done += ring_.read(data + done, count - done);
+            if (done < count) std::this_thread::sleep_for(kPollInterval);
+        }
+        return done;
+    }
+
+    /** Blocks until all samples are queued for playback, or the line closes. */
+    void write(const int16_t *data, size_t count) {
+        size_t done = 0;
+        while (done < count && !closing_.load()) {
+            done += ring_.write(data + done, count - done);
+            if (done < count) std::this_thread::sleep_for(kPollInterval);
+        }
+    }
+
+    void close() {
+        closing_.store(true);
+        std::lock_guard<std::mutex> lock(mutex_);
+        if (stream_) {
+            stream_->stop();
+            stream_->close();
+            stream_.reset();
+        }
+    }
+
+    oboe::DataCallbackResult onAudioReady(oboe::AudioStream *, void *audioData, int32_t numFrames) override {
+        auto *samples = static_cast<int16_t *>(audioData);
+        size_t count = static_cast<size_t>(numFrames) * channels_;
+        if (input_) {
+            ring_.write(samples, count);  // a reader that fell behind loses the newest audio
+        } else {
+            size_t played = ring_.read(samples, count);
+            if (played < count) std::memset(samples + played, 0, (count - played) * sizeof(int16_t));
+        }
+        return oboe::DataCallbackResult::Continue;
+    }
+
+    /** The device went away (headset unplugged, route changed): follow onto the new one. */
+    void onErrorAfterClose(oboe::AudioStream *, oboe::Result error) override {
+        if (closing_.load()) return;
+        __android_log_print(ANDROID_LOG_INFO, kTag, "stream closed (%s), reopening",
+                            oboe::convertToText(error));
+        deviceId_ = 0;
+        if (open() == oboe::Result::OK) start();
+    }
+
+private:
+    const bool input_;
+    int32_t deviceId_;
+    const int32_t channels_;
+    SampleRing ring_;
+    std::atomic<bool> closing_{false};
+    std::mutex mutex_;
+    std::shared_ptr<oboe::AudioStream> stream_;
+};
+
+AudioLine *line(jlong handle) {
+    return reinterpret_cast<AudioLine *>(handle);
+}
+
+thread_local std::vector<int16_t> scratch;
+
+}  // namespace
+
+extern "C" {
+
+JNIEXPORT jlong JNICALL
+Java_com_ts3client_android_audio_OboeLine_nativeOpen(JNIEnv *env, jclass, jboolean input, jint deviceId,
+                                                     jint channels) {
+    auto *created = new AudioLine(input, deviceId, channels);
+    oboe::Result result = created->open();
+    if (result != oboe::Result::OK) {
+        delete created;
+        env->ThrowNew(env->FindClass("java/lang/IllegalStateException"), oboe::convertToText(result));
+        return 0;
+    }
+    return reinterpret_cast<jlong>(created);
+}
+
+JNIEXPORT jint JNICALL
+Java_com_ts3client_android_audio_OboeLine_nativeChannels(JNIEnv *, jclass, jlong handle) {
+    return line(handle)->channels();
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_OboeLine_nativeStart(JNIEnv *env, jclass, jlong handle) {
+    oboe::Result result = line(handle)->start();
+    if (result != oboe::Result::OK) {
+        env->ThrowNew(env->FindClass("java/lang/IllegalStateException"), oboe::convertToText(result));
+    }
+}
+
+JNIEXPORT jint JNICALL
+Java_com_ts3client_android_audio_OboeLine_nativeRead(JNIEnv *env, jclass, jlong handle, jbyteArray buffer,
+                                                     jint offset, jint length) {
+    size_t samples = static_cast<size_t>(length) / sizeof(int16_t);
+    scratch.resize(samples);
+    size_t read = line(handle)->read(scratch.data(), samples);
+    env->SetByteArrayRegion(buffer, offset, static_cast<jsize>(read * sizeof(int16_t)),
+                            reinterpret_cast<const jbyte *>(scratch.data()));
+    return static_cast<jint>(read * sizeof(int16_t));
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_OboeLine_nativeWrite(JNIEnv *env, jclass, jlong handle, jbyteArray buffer,
+                                                      jint offset, jint length) {
+    size_t samples = static_cast<size_t>(length) / sizeof(int16_t);
+    scratch.resize(samples);
+    env->GetByteArrayRegion(buffer, offset, static_cast<jsize>(samples * sizeof(int16_t)),
+                            reinterpret_cast<jbyte *>(scratch.data()));
+    line(handle)->write(scratch.data(), samples);
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_OboeLine_nativeClose(JNIEnv *, jclass, jlong handle) {
+    line(handle)->close();
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_OboeLine_nativeDelete(JNIEnv *, jclass, jlong handle) {
+    delete line(handle);
+}
+
+}  // extern "C"

android/audio/src/main/cpp/opus_jni.cpp

@@ -0,0 +1,109 @@
+// libopus for NativeOpus: handles are the raw encoder/decoder pointers.
+
+#include <jni.h>
+#include <opus.h>
+
+#include <string>
+#include <vector>
+
+namespace {
+
+constexpr int kMaxPacketBytes = 4096;
+
+void throwOpus(JNIEnv *env, const char *call, int error) {
+    std::string message = std::string(call) + " failed: " + opus_strerror(error);
+    env->ThrowNew(env->FindClass("java/lang/IllegalStateException"), message.c_str());
+}
+
+OpusEncoder *encoder(jlong handle) { return reinterpret_cast<OpusEncoder *>(handle); }
+
+OpusDecoder *decoder(jlong handle) { return reinterpret_cast<OpusDecoder *>(handle); }
+
+}  // namespace
+
+extern "C" {
+
+JNIEXPORT jlong JNICALL
+Java_com_ts3client_android_audio_NativeOpus_encoderCreate(JNIEnv *env, jclass, jint sampleRate, jint channels,
+                                                          jint application) {
+    int error = OPUS_OK;
+    OpusEncoder *created = opus_encoder_create(sampleRate, channels, application, &error);
+    if (error != OPUS_OK) {
+        throwOpus(env, "opus_encoder_create", error);
+        return 0;
+    }
+    return reinterpret_cast<jlong>(created);
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_NativeOpus_encoderCtl(JNIEnv *env, jclass, jlong handle, jint request,
+                                                       jint value) {
+    int result = opus_encoder_ctl(encoder(handle), request, value);
+    if (result < 0) throwOpus(env, "opus_encoder_ctl", result);
+}
+
+JNIEXPORT jbyteArray JNICALL
+Java_com_ts3client_android_audio_NativeOpus_encode(JNIEnv *env, jclass, jlong handle, jfloatArray pcm,
+                                                   jint frameSize) {
+    unsigned char packet[kMaxPacketBytes];
+    jfloat *samples = env->GetFloatArrayElements(pcm, nullptr);
+    int length = opus_encode_float(encoder(handle), samples, frameSize, packet, kMaxPacketBytes);
+    env->ReleaseFloatArrayElements(pcm, samples, JNI_ABORT);
+    if (length < 0) {
+        throwOpus(env, "opus_encode_float", length);
+        return nullptr;
+    }
+    jbyteArray out = env->NewByteArray(length);
+    env->SetByteArrayRegion(out, 0, length, reinterpret_cast<const jbyte *>(packet));
+    return out;
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_NativeOpus_encoderDestroy(JNIEnv *, jclass, jlong handle) {
+    opus_encoder_destroy(encoder(handle));
+}
+
+JNIEXPORT jlong JNICALL
+Java_com_ts3client_android_audio_NativeOpus_decoderCreate(JNIEnv *env, jclass, jint sampleRate, jint channels) {
+    int error = OPUS_OK;
+    OpusDecoder *created = opus_decoder_create(sampleRate, channels, &error);
+    if (error != OPUS_OK) {
+        throwOpus(env, "opus_decoder_create", error);
+        return 0;
+    }
+    return reinterpret_cast<jlong>(created);
+}
+
+/** Decodes {@code packet}, or conceals {@code frameSize} samples when it is null. */
+JNIEXPORT jint JNICALL
+Java_com_ts3client_android_audio_NativeOpus_decode(JNIEnv *env, jclass, jlong handle, jbyteArray packet,
+                                                   jfloatArray out, jint frameSize) {
+    std::vector<unsigned char> data;
+    if (packet != nullptr) {
+        data.resize(static_cast<size_t>(env->GetArrayLength(packet)));
+        env->GetByteArrayRegion(packet, 0, static_cast<jsize>(data.size()), reinterpret_cast<jbyte *>(data.data()));
+    }
+    jfloat *samples = env->GetFloatArrayElements(out, nullptr);
+    int decoded = opus_decode_float(decoder(handle), packet != nullptr ? data.data() : nullptr,
+                                    static_cast<opus_int32>(data.size()), samples, frameSize, 0);
+    env->ReleaseFloatArrayElements(out, samples, decoded < 0 ? JNI_ABORT : 0);
+    if (decoded < 0) throwOpus(env, "opus_decode_float", decoded);
+    return decoded;
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_NativeOpus_decoderReset(JNIEnv *, jclass, jlong handle) {
+    opus_decoder_ctl(decoder(handle), OPUS_RESET_STATE);
+}
+
+JNIEXPORT void JNICALL
+Java_com_ts3client_android_audio_NativeOpus_decoderDestroy(JNIEnv *, jclass, jlong handle) {
+    opus_decoder_destroy(decoder(handle));
+}
+
+JNIEXPORT jstring JNICALL
+Java_com_ts3client_android_audio_NativeOpus_version0(JNIEnv *env, jclass) {
+    return env->NewStringUTF(opus_get_version_string());
+}
+
+}  // extern "C"

android/audio/src/main/java/com/ts3client/android/audio/AndroidAudioBackend.java

@@ -0,0 +1,40 @@
+package com.ts3client.android.audio;
+
+import android.content.Context;
+
+import com.ts3client.audio.AudioBackend;
+import com.ts3client.audio.AudioIo;
+import com.ts3client.audio.StreamingVoiceOutput;
+import com.ts3client.audio.opus.OpusCodec;
+
+/** Android's audio stack: Oboe for the devices, libopus built with the NDK. */
+public final class AndroidAudioBackend implements AudioBackend {
+
+    private final AudioIo io;
+    private final OpusCodec opus = new NativeOpus();
+
+    public AndroidAudioBackend(Context context) {
+        this.io = new AndroidAudioIo(context.getApplicationContext());
+    }
+
+    @Override
+    public AudioIo io() {
+        return io;
+    }
+
+    @Override
+    public OpusCodec opus() {
+        return opus;
+    }
+
+    /** One low-latency stream for everyone, as mobile audio wants. */
+    @Override
+    public StreamingVoiceOutput.Lines outputLines() {
+        return StreamingVoiceOutput.Lines.SHARED;
+    }
+
+    @Override
+    public String description() {
+        return "Opus " + opus.version() + ", Oboe";
+    }
+}

android/audio/src/main/java/com/ts3client/android/audio/AndroidAudioIo.java

@@ -0,0 +1,86 @@
+package com.ts3client.android.audio;
+
+import android.content.Context;
+import android.media.AudioDeviceInfo;
+import android.media.AudioManager;
+
+import com.ts3client.audio.AudioCapture;
+import com.ts3client.audio.AudioDevice;
+import com.ts3client.audio.AudioIo;
+import com.ts3client.audio.AudioPlayback;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** The device's microphones and speakers, opened through Oboe. Device ids are Android's. */
+final class AndroidAudioIo implements AudioIo {
+
+    private final AudioManager audioManager;
+
+    AndroidAudioIo(Context context) {
+        this.audioManager = context.getSystemService(AudioManager.class);
+    }
+
+    @Override
+    public List<AudioDevice> inputDevices() {
+        return devices(AudioManager.GET_DEVICES_INPUTS);
+    }
+
+    @Override
+    public List<AudioDevice> outputDevices() {
+        return devices(AudioManager.GET_DEVICES_OUTPUTS);
+    }
+
+    private List<AudioDevice> devices(int flags) {
+        List<AudioDevice> out = new ArrayList<>();
+        out.add(AudioDevice.DEFAULT);
+        for (AudioDeviceInfo info : audioManager.getDevices(flags)) {
+            out.add(new AudioDevice(Integer.toString(info.getId()), info.getProductName() + " (" + typeName(info) + ")"));
+        }
+        return out;
+    }
+
+    @Override
+    public AudioCapture openCapture(String deviceId, int preferredChannels) {
+        return OboeLine.capture(parseId(deviceId), preferredChannels);
+    }
+
+    @Override
+    public AudioPlayback openPlayback(String deviceId, int preferredChannels) {
+        return OboeLine.playback(parseId(deviceId), preferredChannels);
+    }
+
+    /** 0 lets the system choose, as it does for the default device. */
+    private static int parseId(String deviceId) {
+        try {
+            return deviceId == null || deviceId.isEmpty() ? 0 : Integer.parseInt(deviceId);
+        } catch (NumberFormatException e) {
+            return 0;
+        }
+    }
+
+    private static String typeName(AudioDeviceInfo info) {
+        switch (info.getType()) {
+            case AudioDeviceInfo.TYPE_BUILTIN_MIC:
+                return "built-in microphone";
+            case AudioDeviceInfo.TYPE_BUILTIN_SPEAKER:
+                return "speaker";
+            case AudioDeviceInfo.TYPE_BUILTIN_EARPIECE:
+                return "earpiece";
+            case AudioDeviceInfo.TYPE_WIRED_HEADSET:
+                return "wired headset";
+            case AudioDeviceInfo.TYPE_WIRED_HEADPHONES:
+                return "wired headphones";
+            case AudioDeviceInfo.TYPE_USB_HEADSET:
+            case AudioDeviceInfo.TYPE_USB_DEVICE:
+                return "USB";
+            case AudioDeviceInfo.TYPE_BLUETOOTH_SCO:
+            case AudioDeviceInfo.TYPE_BLUETOOTH_A2DP:
+            case AudioDeviceInfo.TYPE_BLE_HEADSET:
+            case AudioDeviceInfo.TYPE_BLE_SPEAKER:
+                return "Bluetooth";
+            default:
+                return "type " + info.getType();
+        }
+    }
+}

android/audio/src/main/java/com/ts3client/android/audio/NativeOpus.java

@@ -0,0 +1,114 @@
+package com.ts3client.android.audio;
+
+import com.ts3client.audio.opus.CtlOpusEncoder;
+import com.ts3client.audio.opus.LibOpus;
+import com.ts3client.audio.opus.OpusCodec;
+import com.ts3client.audio.opus.OpusDecoder;
+import com.ts3client.audio.opus.OpusEncoder;
+
+/** libopus, built into the app with the NDK. */
+public final class NativeOpus implements OpusCodec {
+
+    static {
+        System.loadLibrary("ts3audio");
+    }
+
+    @Override
+    public OpusEncoder createEncoder(int sampleRate, int frameSize, int channels, Application application) {
+        return new Encoder(encoderCreate(sampleRate, channels, LibOpus.application(application)), frameSize);
+    }
+
+    @Override
+    public OpusDecoder createDecoder(int sampleRate, int maxFrameSize, int channels) {
+        return new Decoder(decoderCreate(sampleRate, channels), maxFrameSize);
+    }
+
+    @Override
+    public String version() {
+        return version0();
+    }
+
+    /** Methods may come from different threads, one at a time, so they only share the handle. */
+    private static final class Encoder extends CtlOpusEncoder {
+        private final int frameSize;
+        private long handle;
+
+        Encoder(long handle, int frameSize) {
+            this.handle = handle;
+            this.frameSize = frameSize;
+        }
+
+        @Override
+        protected synchronized void ctl(int request, int value) {
+            if (handle != 0) encoderCtl(handle, request, value);
+        }
+
+        @Override
+        public synchronized byte[] encode(float[] pcm) {
+            if (handle == 0) throw new IllegalStateException("encoder closed");
+            return NativeOpus.encode(handle, pcm, frameSize);
+        }
+
+        @Override
+        public synchronized void close() {
+            if (handle == 0) return;
+            encoderDestroy(handle);
+            handle = 0;
+        }
+    }
+
+    private static final class Decoder implements OpusDecoder {
+        private final int maxFrameSize;
+        private long handle;
+
+        Decoder(long handle, int maxFrameSize) {
+            this.handle = handle;
+            this.maxFrameSize = maxFrameSize;
+        }
+
+        @Override
+        public int decode(byte[] packet, float[] out) {
+            return NativeOpus.decode(live(), packet, out, maxFrameSize);
+        }
+
+        @Override
+        public int conceal(float[] out, int frameSize) {
+            return NativeOpus.decode(live(), null, out, Math.min(frameSize, maxFrameSize));
+        }
+
+        @Override
+        public void reset() {
+            if (handle != 0) decoderReset(handle);
+        }
+
+        @Override
+        public void close() {
+            if (handle == 0) return;
+            decoderDestroy(handle);
+            handle = 0;
+        }
+
+        private long live() {
+            if (handle == 0) throw new IllegalStateException("decoder closed");
+            return handle;
+        }
+    }
+
+    private static native long encoderCreate(int sampleRate, int channels, int application);
+
+    private static native void encoderCtl(long handle, int request, int value);
+
+    private static native byte[] encode(long handle, float[] pcm, int frameSize);
+
+    private static native void encoderDestroy(long handle);
+
+    private static native long decoderCreate(int sampleRate, int channels);
+
+    private static native int decode(long handle, byte[] packet, float[] out, int frameSize);
+
+    private static native void decoderReset(long handle);
+
+    private static native void decoderDestroy(long handle);
+
+    private static native String version0();
+}

android/audio/src/main/java/com/ts3client/android/audio/OboeLine.java

@@ -0,0 +1,91 @@
+package com.ts3client.android.audio;
+
+import com.ts3client.audio.AudioCapture;
+import com.ts3client.audio.AudioPlayback;
+
+/**
+ * An Oboe stream, as either an {@link AudioCapture} or an {@link AudioPlayback}. The native
+ * side keeps a ring between the real-time callback and these blocking calls.
+ */
+final class OboeLine implements AudioCapture, AudioPlayback {
+
+    static {
+        System.loadLibrary("ts3audio");
+    }
+
+    /** Held across native reads and writes, so {@link #close} never frees a line in use. */
+    private final Object io = new Object();
+    private final int channels;
+    private volatile long handle;
+
+    private OboeLine(boolean input, int deviceId, int channels) {
+        this.handle = nativeOpen(input, deviceId, channels);
+        this.channels = nativeChannels(handle);
+    }
+
+    static OboeLine capture(int deviceId, int channels) {
+        return new OboeLine(true, deviceId, channels);
+    }
+
+    static OboeLine playback(int deviceId, int channels) {
+        return new OboeLine(false, deviceId, channels);
+    }
+
+    @Override
+    public int channels() {
+        return channels;
+    }
+
+    @Override
+    public void start() {
+        long h = handle;
+        if (h != 0) nativeStart(h);
+    }
+
+    @Override
+    public int read(byte[] buffer, int offset, int length) {
+        synchronized (io) {
+            long h = handle;
+            return h == 0 ? 0 : nativeRead(h, buffer, offset, length);
+        }
+    }
+
+    @Override
+    public void write(byte[] buffer, int offset, int length) {
+        synchronized (io) {
+            long h = handle;
+            if (h != 0) nativeWrite(h, buffer, offset, length);
+        }
+    }
+
+    /** Oboe has no drain; what is queued is at most a few frames and simply plays out. */
+    @Override
+    public void drain() {
+    }
+
+    @Override
+    public void close() {
+        long h = handle;
+        if (h == 0) return;
+        nativeClose(h); // wakes a blocked read or write
+        synchronized (io) {
+            if (handle == 0) return;
+            handle = 0;
+            nativeDelete(h);
+        }
+    }
+
+    private static native long nativeOpen(boolean input, int deviceId, int channels);
+
+    private static native int nativeChannels(long handle);
+
+    private static native void nativeStart(long handle);
+
+    private static native int nativeRead(long handle, byte[] buffer, int offset, int length);
+
+    private static native void nativeWrite(long handle, byte[] buffer, int offset, int length);
+
+    private static native void nativeClose(long handle);
+
+    private static native void nativeDelete(long handle);
+}

android/build.gradle.kts

@@ -0,0 +1,5 @@
+plugins {
+    alias(libs.plugins.android.application) apply false
+    alias(libs.plugins.android.library) apply false
+    alias(libs.plugins.kotlin.compose) apply false
+}

android/core/build.gradle.kts

@@ -0,0 +1,17 @@
+plugins {
+    `java-library`
+}
+
+java {
+    sourceSets["main"].java.setSrcDirs(listOf(rootDir.resolve("../ts3-client/core/src/main/java")))
+    sourceSets["main"].resources.setSrcDirs(listOf(rootDir.resolve("../ts3-client/core/src/main/resources")))
+}
+
+tasks.withType<JavaCompile>().configureEach {
+    options.release = 17
+    options.encoding = "UTF-8"
+}
+
+dependencies {
+    api(project(":ts3j"))
+}

android/gradle.properties

@@ -0,0 +1,4 @@
+org.gradle.jvmargs=-Xmx4g -Dfile.encoding=UTF-8
+org.gradle.parallel=true
+org.gradle.configuration-cache=true
+android.useAndroidX=true

android/gradle/libs.versions.toml

@@ -0,0 +1,25 @@
+[versions]
+agp = "9.4.1"
+kotlin = "2.4.20"
+composeBom = "2026.09.00"
+activityCompose = "1.13.0"
+lifecycle = "2.11.0"
+bouncycastle = "1.86"
+ini4j = "0.5.1"
+oboe = "1.11.0"
+
+[libraries]
+androidx-activity-compose = { module = "androidx.activity:activity-compose", version.ref = "activityCompose" }
+androidx-compose-bom = { module = "androidx.compose:compose-bom", version.ref = "composeBom" }
+androidx-compose-material3 = { module = "androidx.compose.material3:material3" }
+androidx-compose-ui = { module = "androidx.compose.ui:ui" }
+androidx-lifecycle-runtime-compose = { module = "androidx.lifecycle:lifecycle-runtime-compose", version.ref = "lifecycle" }
+androidx-lifecycle-viewmodel-compose = { module = "androidx.lifecycle:lifecycle-viewmodel-compose", version.ref = "lifecycle" }
+bouncycastle = { module = "org.bouncycastle:bcprov-jdk18on", version.ref = "bouncycastle" }
+ini4j = { module = "org.ini4j:ini4j", version.ref = "ini4j" }
+oboe = { module = "com.google.oboe:oboe", version.ref = "oboe" }
+
+[plugins]
+android-application = { id = "com.android.application", version.ref = "agp" }
+android-library = { id = "com.android.library", version.ref = "agp" }
+kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }

android/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,9 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.8.0-bin.zip
+networkTimeout=10000
+retries=0
+retryBackOffMs=500
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

android/gradlew

@@ -0,0 +1,248 @@
+#!/bin/sh
+
+#
+# Copyright © 2015 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+##############################################################################
+#
+#   gradlew start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh gradlew
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/3d91ce3b8caaf77ad09f381f43615b715b53f72c/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s\n' "$PWD" ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

android/gradlew.bat

@@ -0,0 +1,112 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  gradlew startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables, and ensure extensions are enabled
+setlocal EnableExtensions
+
+@rem Catch executions from older scripts and ensure they exit cleanly.
+@rem This can be removed once we can be reasonably confident that few people
+@rem will be migrating directly to this new wrapper.
+goto afterSafetyNet
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
+goto exitWithErrorLevel
+:afterSafetyNet
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+1>&2 echo.
+1>&2 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+1>&2 echo.
+1>&2 echo Please set the JAVA_HOME variable in your environment to match the
+1>&2 echo location of your Java installation.
+
+"%COMSPEC%" /c exit 1
+goto exitWithErrorLevel
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+1>&2 echo.
+1>&2 echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+1>&2 echo.
+1>&2 echo Please set the JAVA_HOME variable in your environment to match the
+1>&2 echo location of your Java installation.
+
+"%COMSPEC%" /c exit 1
+goto exitWithErrorLevel
+
+:execute
+@rem Setup the command line
+
+
+
+@rem Execute gradlew
+@rem endlocal doesn't take effect until after the line is parsed and variables are expanded
+@rem which allows us to clear the local environment before executing the java command
+endlocal & "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %* & call :exitWithErrorLevel & goto exitWithErrorLevel
+
+@rem This label must not be changed. We rely on old scripts being able to jump to this point.
+:exitWithErrorLevel
+@rem Use "%COMSPEC%" /c exit to allow operators to work properly in scripts
+"%COMSPEC%" /c exit %ERRORLEVEL%

android/settings.gradle.kts

@@ -0,0 +1,20 @@
+pluginManagement {
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+rootProject.name = "ts3-android"
+
+// core and ts3j compile the very sources the desktop's Maven build does.
+include(":ts3j", ":core", ":audio", ":app")

android/ts3j/build.gradle.kts

@@ -0,0 +1,18 @@
+plugins {
+    `java-library`
+}
+
+java {
+    sourceSets["main"].java.setSrcDirs(listOf(rootDir.resolve("../ts3j/src/main/java")))
+}
+
+tasks.withType<JavaCompile>().configureEach {
+    options.release = 17
+    options.encoding = "UTF-8"
+}
+
+dependencies {
+    // Android ships a BouncyCastle of its own, but under a different package, so they never meet.
+    api(libs.bouncycastle)
+    api(libs.ini4j)
+}