How It Works — BuddyDoggie

📡 The Short Answer

Your phone continuously broadcasts a small BLE advertisement packet containing your pet's ID, type, and level. Other phones running BuddyDoggie that are within Bluetooth range (~30 meters) pick up this broadcast, and vice versa. When both devices discover each other, the app logs a StreetPass encounter — exactly like the Nintendo 3DS did with its hardware-based StreetPass, but using standard BLE that works on any modern smartphone.

📱 🐕 Mochi Your phone

〰️

BLE Advertisement

📱 🐈 Luna Other player

🔬 Step by Step

1

Your Phone Broadcasts

When BuddyDoggie runs in the background, it starts a BLE peripheral that advertises a small payload (~20 bytes) every 100-300ms. This payload contains an anonymous pet ID hash, species code, and level — no personal data.

2

Other Phones Scan

Every other BuddyDoggie user nearby is also advertising and scanning. When their phone sees your advertisement, it recognizes the BuddyDoggie service UUID (0xFEED) and flags it as a discovery.

3

Handshake & Card Exchange

Both devices initiate a brief BLE GATT connection to exchange richer pet card data — name, avatar, outfit, and a greeting message. This takes ~1-2 seconds and doesn't require internet.

4

Notification & Collection

When you next open BuddyDoggie, you see: "Mochi met Luna on Maple Street!" with the pet's card added to your collection. You can send them a gift, visit their profile, or set them up to play together.

🎮 Like the 3DS, But Smarter

The original Nintendo 3DS used dedicated 2.4 GHz wireless hardware for StreetPass — it worked even in sleep mode. BuddyDoggie achieves the same magic using BLE, which is designed exactly for this kind of low-power, always-on discovery.

	3DS StreetPass	BuddyDoggie (BLE)
Wireless Tech	Proprietary 2.4 GHz	Bluetooth Low Energy 5.0+
Range	10-20 meters	~30 meters (BLE 5.0)
Background Mode	Sleep mode works	App runs in background
Data Exchanged	Mii, game data	Pet card, greeting, gifts
Max Encounters/Day	12 (3DS limit)	Unlimited
Internet Required	No	No (BLE only)

💻 Under the Hood

Here's a simplified view of how BuddyDoggie sets up BLE advertising:

// 1. Create BLE advertisement payload (~20 bytes)
const payload = encodePetData({
  petId:    hash(user.uuid + "buddydoggie"),
  species:  "golden_retriever",
  level:    12,
  mood:     "happy",
});

// 2. Start advertising with BuddyDoggie service UUID
const advertiser = BleManager.createAdvertiser({
  serviceUuid: "0xFEED",  // BuddyDoggie assigned UUID
  payload: payload,
  interval: 200,           // ms between advertisements
  txPower: -4,             // dBm, balances range vs battery
});
advertiser.start();

// 3. Scan for other BuddyDoggie devices
const scanner = BleManager.createScanner({
  serviceUuids: ["0xFEED"],
  allowDuplicates: false,
});
scanner.onDiscovered((device) => {
  const pet = decodePetData(device.adPayload);
  logStreetPass(pet, device.rssi);  // estimate proximity
  connectGATT(device);              // exchange full cards
});
scanner.start();
    

The entire BLE stack uses less than 1% battery per hour of background advertising, making it practical for all-day StreetPass discovery without draining your phone.

🔒 Privacy & Safety

StreetPass is designed from the ground up to keep you anonymous:

Pet IDs are one-way hashed — they can't be reversed to find your identity
No GPS location is transmitted — proximity is estimated from BLE signal strength only
Advertisements contain no name, email, phone number, or account data
You can pause StreetPass at any time from settings
Encounter logs are stored locally and only sync to the cloud when you open the app
Full card exchange requires mutual discovery — both devices must see each other

How Does StreetPass Work?