# `Mob.Bt.Spp`
[🔗](https://github.com/genericjam/mob/blob/master/lib/mob/bt/spp.ex#L1)

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.

# `connect`

```elixir
@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`

```elixir
@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).

---

*Consult [api-reference.md](api-reference.md) for complete listing*