Telemetry — LAN + Cloud Push-to-Talk

Android walkie-talkie with two transports behind one TalkNet UI:

• LAN Direct — phone-to-phone voice over local WiFi (UDP, no internet, no account)
• Cloud Channels — internet rooms via LiveKit Cloud (SFU), any word is a room

Everything audio runs in a foreground service, so it keeps talking with the screen off.

Features

Talk

• Hold-to-talk everywhere (big round PTT), volume-down PTT, Live monitor mode (mic stays open)
• LAN: 16 kHz PCM over UDP :50005; Cloud: Opus over LiveKit WebRTC, mic muted by default

Channels

• Home lists pinned rooms (Office / Warehouse / Remote / Security), recent rooms, and JOIN BY WORD — any word is a channel, no creation step
• Room names validated like the server (letters, numbers, space, _ or -, max 64)

Discovery & presence (LAN)

• UDP broadcast beacons (:50006, every 2s): name + IP + battery, 10s expiry
• NEARBY lists with avatars, battery %, staleness, tap-to-dial; manual IP fallback
• Multi-homed phones beacon per interface; hotspot-aware own-IP picking

Messaging & health

• Quick texts (presets, one per line, max 8): LiveKit data messages on Cloud, TXT| sidecar packets on LAN
• Connection-quality dots on cloud avatars (mint / amber / red)

Platform

• Foreground service (microphone type) with sticky notification + Stop action — keeps talking with the screen off
• First-launch onboarding: Welcome → Permissions (with rationale) → Battery exemption → Done; the service never starts before onboarding completes
• Android 14+ safe: idles as a mediaPlayback service and escalates to the mic type only while transmitting, so a fresh install without mic permission can't crash it
• Jetpack Compose + Material 3 Expressive dark TalkNet theme
• App icon: mint mic + telemetry waves adaptive icon on #14262A (incl. monochrome themed-icon variant)

Using the app

1. Install app-release.apk from Releases (release-signed).
2. Grant Microphone (and Notifications on Android 13+) when asked; accept the battery-optimization prompt so it works screen-off.
3. LAN: open the LAN tab, set your name, tap a NEARBY peer (or type an IP), open LAN Talk, hold to talk. Both phones must be on the same WiFi (or one phone's hotspot). Guest WiFis with client isolation block device-to-device traffic — use the main SSID or hotspot mode.
4. Cloud: open the CLOUD tab → + Join → name + channel → Join. First run needs the LiveKit URL + token-server URL (Server settings). Hold to talk.

Token server (Cloud mode only)

The app never holds the LiveKit API secret. A tiny Cloudflare Worker mints short-lived join tokens. Full setup: token-server/README.md.

cd token-server
wrangler secret put LIVEKIT_API_KEY
wrangler secret put LIVEKIT_API_SECRET
wrangler deploy

Build from source

Android Studio (recommended): open the telemetry folder → Trust Project → wait for Gradle sync → Run (Shift+F10) on an emulator or USB device.

Command line: needs AGP 9.x-compatible Gradle (9.5+) and the Studio-bundled JDK:

$env:JAVA_HOME = "C:\Program Files\Android\Android Studio\jbr"
$env:ANDROID_HOME = "$env:LOCALAPPDATA\Android\Sdk"
& "$env:USERPROFILE\.gradle\wrapper\dists\gradle-9.5.0-bin\<hash>\gradle-9.5.0\bin\gradle.bat" :app:assembleDebug

APK lands at app/build/outputs/apk/debug/app-debug.apk (debug-signed).

Official release build (signed)

Release builds are signed with app/telemetry-release.jks (4096-bit RSA, 30-year validity). Credentials live in keystore.properties at the repo root, which is gitignored and never committed:

storeFile=app/telemetry-release.jks
storePassword=...
keyAlias=telemetry
keyPassword=...

$env:JAVA_HOME = "C:\Program Files\Android\Android Studio\jbr"
$env:ANDROID_HOME = "$env:LOCALAPPDATA\Android\Sdk"
& "$env:USERPROFILE\.gradle\wrapper\dists\gradle-9.5.0-bin\<hash>\gradle-9.5.0\bin\gradle.bat" :app:assembleRelease :app:bundleRelease

This produces a release-signed APK at app/build/outputs/apk/release/app-release.apk and an upload bundle at app/build/outputs/bundle/release/app-release.aab (APK Signature Scheme v2; verify with apksigner verify --verbose --print-certs). The build fails fast with a clear message if keystore.properties is missing, so a release can never silently ship with a debug signature. Back up app/telemetry-release.jks plus keystore.properties somewhere safe (password manager + offline copy) — lose the key and Play Store updates for this app id become impossible.

Permissions (and why you’ll be asked)

Permission	Why
RECORD_AUDIO	Mic for voice
FOREGROUND_SERVICE + FOREGROUND_SERVICE_MICROPHONE	Keep voice alive screen-off
POST_NOTIFICATIONS	Foreground-service notification (Android 13+)
INTERNET / ACCESS_NETWORK_STATE	Cloud voice + token fetch
ACCESS_WIFI_STATE / CHANGE_WIFI_MULTICAST_STATE	LAN discovery broadcasts
Battery-optimization exemption (prompted once)	Survive Doze while listening

Known limits

• No end-to-end encryption (LiveKit transport security only; LAN is raw PCM).
• Guest/isolated WiFis block LAN entirely — hotspot mode is the fallback.
• No background-service exemption handling beyond the first-run prompt.