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# Mob.Bt.Spp (mob v0.6.18)

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Bluetooth Classic Serial Port Profile (SPP) — RFCOMM byte streams.

Use this for legacy serial-over-Bluetooth devices: Arduino HC-05/HC-06 modules, OBD-II ELM327 readers, marine GPS pucks, industrial sensors, legacy barcode scanners, etc. Anything that exposes itself as a bidirectional byte pipe over a custom RFCOMM channel UUID.

See `Mob.Bt` for pairing, discovery, and disconnect.

## Typical flow

    # 1. Pair (Mob.Bt.pair/2)

    # 2. Connect SPP, supplying the RFCOMM service UUID.
    #    The well-known SPP UUID is "00001101-0000-1000-8000-00805F9B34FB".
    socket = Mob.Bt.Spp.connect(socket, device,
               uuid: "00001101-0000-1000-8000-00805F9B34FB")
    # {:bt, :spp_connected, session_id, device}

    # 3. Receive bytes:
    # {:bt, :spp_data, session_id, bytes}

    # 4. Send bytes:
    Mob.Bt.Spp.write(socket, session_id, "ATZ\r\n")

    # 5. Disconnect (Mob.Bt.disconnect/2)

## UUIDs

Most SPP devices advertise the standard SPP UUID `00001101-0000-1000-8000-00805F9B34FB`. Some manufacturers use custom UUIDs to scope to a specific protocol on the same physical device. Pass via the `:uuid` opt; if omitted, the standard SPP UUID is used.

## Insecure RFCOMM

By default the connection uses the secure RFCOMM channel (encrypted, requires bond). Some legacy devices (especially HC-06 clones) only accept insecure RFCOMM. Pass `secure: false` to fall back.

## Summary

### Functions

connect(socket, device, opts \\ [])

Open an SPP (RFCOMM) connection to `device`.

write(socket, session_id, bytes)

Write a byte payload to the SPP session.

## Functions

# connect(socket, device, opts \\ [])

    @spec connect(socket :: term(), Mob.Bt.device(), keyword()) :: term()

Open an SPP (RFCOMM) connection to `device`.

## Options

- `:uuid` — RFCOMM service UUID (default: `"00001101-0000-1000-8000-00805F9B34FB"`)
- `:secure` — `true` (default, encrypted) or `false` (legacy insecure)

Result: `{:bt, :spp_connected, session_id, device}` on success, `{:bt, :spp_connect_failed, nil, %{device: device, reason: atom()}}` on failure.

# write(socket, session_id, bytes)

    @spec write(socket :: term(), Mob.Bt.session_id(), binary()) :: term()

Write a byte payload to the SPP session.

Returns the socket. Fire-and-forget: bytes are queued in Kotlin's output stream and flushed asynchronously. No completion event.

Errors during write are surfaced as `{:bt, :spp_disconnected, session_id, reason}` (Kotlin closes the socket on write failure).