Mesh

Nearby phone chat over Bluetooth. No internet, no pairing, no account.

Android phones talk over a BitChat-style BLE mesh. A Windows laptop can still join over classic Bluetooth.

What it does

• Finds phones around you automatically (no pairing for phone-to-phone chat).
• Sends messages and files while you stay in the app.
• Relays through nearby phones when a direct link is not enough.
• Signs chat and files so relays cannot undetectably tamper with payloads. Messages are not end-to-end encrypted; nearby radios and relays can read them.

Project notes

• Package: com.devil1716.bluetoothmanet
• Language: Java + Kotlin
• Launcher: ComposeMeshActivity (legacy XML console is MainActivity, hidden behind a long-press on the version in Settings → About)
• Min SDK: 21
• Target / Compile SDK: 34
• Current release: v1.4.4
• Android Gradle Plugin: 8.5.2

How to run

1. Open the project in Android Studio.
2. Build and run on at least 2 Android phones.
3. On each phone:
   • Allow Bluetooth when asked. Turn Location on if the banner says so.
   • Nearby chat starts on its own after permission. If not, tap Start nearby chat.
   • Share your ID, tap someone under Online, or use New chat.
4. Send a message. Laptop / already-paired devices live under Settings → Advanced.

Multi-hop test

• Phone A links to Phone B, Phone B links to Phone C.
• Send from A to C.
• B forwards automatically.

Important limitations

• Keep the app in the foreground (or the Mesh is on notification) so Android does not freeze Bluetooth.
• Location must be on for nearby scanning on many devices.
• Phones usually need to be paired first only for a Windows laptop.
• Received files land in the app-specific Downloads directory, not the system Downloads list.

Updating Mesh

From 1.3.6 on, GitHub APKs are signed with a stable key and the app updates in place (WhatsApp-style banner: download, then Install).

If you still have 1.3.5 or an Android Studio debug build, Android will refuse the new APK as a package conflict. Copy your ID, uninstall Mesh, then install the latest release. After that, in-app updates replace the existing app.

Windows laptop node

If you want the Windows laptop to join, use the Python CLI in windows-node. That path still uses classic Bluetooth.

Architecture

BLE mesh, flood routing, presence hellos, and store-and-forward are documented in docs/ARCHITECTURE.md. Threats and identity limits: docs/THREAT_MODEL.md. Signing and the leaked upload key: docs/SIGNING.md. Device tests: docs/HARDWARE_TEST.md.

Publishing a GitHub release

Do not ship app-debug.apk. Configure the Actions secrets described in docs/SIGNING.md, then:

1. Open Actions → Android Release → Run workflow.
2. Set tag to the version tag (example: v1.4.4).
3. The workflow runs unit tests and attaches app-release.apk only when release signing secrets are present.