DroidBridge

Phone can go many place, computer can only go one place, what if I want to connect to bluetooth in place where computer isn't? Answer? Droidbridge.

Building

Requires the Android SDK (command line tools or Android Studio) and JDK 17. Put your SDK path in local.properties:

sdk.dir=/path/to/Android/sdk

Then:

./gradlew assembleDebug

The APK lands at app/build/outputs/apk/debug/app-debug.apk.

Installing

adb install app/build/outputs/apk/debug/app-debug.apk

Launch the app, grant Bluetooth + Location permissions, then tap Start Server. The home screen shows the phone's local URL (e.g. http://192.168.1.100:8765). Keep the app in the foreground — it runs as a foreground service with a persistent notification, so Android won't kill it.

API

Base URL: http://<phone-ip>:8765

All request and response bodies are JSON. Binary payloads are hex-encoded strings (e.g. "00056100008a03").

REST

Method	Path	Body	Description
GET	/status	–	Server status + connected device list
GET	/bonded	–	Enumerate bonded (paired) devices — [{address, name, type}]
GET	/connections	–	Currently-connected addresses — {devices: [addr, ...]}
GET	/services/<address>	–	Discovered services + characteristics for a device (404 until /discover finishes)
POST	/scan/start	{filters?: ["uuid", ...]}	Start a low-latency BLE scan (results stream over WS)
POST	/scan/stop	–	Stop scanning
POST	/connect	{address}	Open a GATT connection
POST	/disconnect	{address}	Drop the GATT connection
POST	/discover	{address}	Kick off service discovery — poll /services/<address> until it returns a populated list
POST	/write	{address, service, characteristic, data, writeType?}	Write a characteristic; blocks until onCharacteristicWrite fires
POST	/read	{address, service, characteristic}	Request a read; the result arrives over WS as a notification event
POST	/notify	{address, service, characteristic, enable}	Enable/disable characteristic notifications (writes CCCD)
POST	/mtu	{address, mtu}	Request an ATT MTU change

Write types (for POST /write):

Value	Android constant	Meaning
1	WRITE_TYPE_NO_RESPONSE	Fire-and-forget; ack is the controller accepting the packet
2	WRITE_TYPE_DEFAULT	Waits for an ATT write response from the peer
4	WRITE_TYPE_SIGNED	Signed write (rare)

WebSocket

Connect to ws://<phone-ip>:8765. Messages are JSON objects with type and data fields:

{"type": "connected", "id": "1739830000000"}
{"type": "notification", "data": {"address": "...", "characteristic": "...", "data": "hex"}}
{"type": "connection",   "data": {"address": "...", "connected": true}}
{"type": "scan",         "data": {"address": "...", "name": "...", "rssi": -50, "manufacturerData": {...}}}

The WebSocket is a broadcast stream — every connected client gets every event. If you need device-scoped filtering, filter on the client.

Keep-alive: NanoWSD closes idle sockets after a few seconds. Clients should send a short text frame (e.g. "ping") every 1–2 seconds to keep the connection open.

Example: reading battery via curl

PHONE=192.168.1.100
ADDR=DE:66:9E:50:8B:74

# Connect and discover
curl -X POST http://$PHONE:8765/connect   -H 'Content-Type: application/json' -d "{\"address\":\"$ADDR\"}"
curl -X POST http://$PHONE:8765/discover  -H 'Content-Type: application/json' -d "{\"address\":\"$ADDR\"}"

# Wait for discovery, then list services
curl http://$PHONE:8765/services/$ADDR

# Enable notifications on a characteristic
curl -X POST http://$PHONE:8765/notify -H 'Content-Type: application/json' -d '{
  "address":        "DE:66:9E:50:8B:74",
  "service":        "bae80001-4f05-4503-8e65-3af1f7329d1f",
  "characteristic": "bae80013-4f05-4503-8e65-3af1f7329d1f",
  "enable":         true
}'

# Send a command (hex-encoded bytes)
curl -X POST http://$PHONE:8765/write -H 'Content-Type: application/json' -d '{
  "address":        "DE:66:9E:50:8B:74",
  "service":        "bae80001-4f05-4503-8e65-3af1f7329d1f",
  "characteristic": "bae80012-4f05-4503-8e65-3af1f7329d1f",
  "data":           "00056100008a03",
  "writeType":      1
}'

Meanwhile on ws://192.168.1.100:8765 you'll see the notification stream from the peer.

Architecture

┌─────────────┐      HTTP + WS      ┌──────────────────┐      BLE      ┌────────────┐
│ Your laptop │ ──────────────────> │ DroidBridge app  │ ────────────> │ Peripheral │
│ (any lang)  │ <────────────────── │ (foreground svc) │ <──────────── │ (ring, etc)│
└─────────────┘                     └──────────────────┘               └────────────┘

Source layout:

app/src/main/java/com/commute773/droidbridge/
├── MainActivity.kt     # start/stop button + status screen
├── BridgeService.kt    # foreground service that owns BleManager + BridgeServer
├── BridgeServer.kt     # NanoHTTPD/NanoWSD routing and event broadcast
└── BleManager.kt       # thin wrapper over BluetoothGatt with per-device write queue

Used by

• g2-kit — drives Even Realities G2 smart glasses over BLE.

If you build something on top of DroidBridge, feel free to open a PR adding it to this list.

License

MIT. See LICENSE.