Android with Linux Bluetooth Communication Example

In this example, we’re going to configure Android device with BT to act as a Serial Port Profile Server, and Linux Phyton app as Serial Port Profile Client

Android

Somewhere withing MainActivity.kt file place this function, and then call it with Context.

@SuppressLint("MissingPermission")
fun startBluetoothServer(ctx: Context) {
    val bm = ctx.getSystemService(BluetoothManager::class.java)
    val ba = bm.adapter
    val bss = ba.listenUsingRfcommWithServiceRecord("CM1", UUID.fromString("a60f35f0-b93a-11de-8a39-08002009c666"))

    val t = Thread {
        val socket = bss.accept()
        Log.i("BT", "Socket accepted")
        while (true) {
            val b = socket.inputStream.read()
            socket.outputStream.write(b)
            Log.i("BT", "read/write $b")
        }
    }
    t.name = "BluetoothSocket"
    t.start()
}

Android Manifest permissions

    <uses-permission android:name="android.permission.BLUETOOTH" />

    <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />

Linux

Here is the complete source of Python client communicating with the Android device.
This assumes that pairing has already been performed.

import socket
from time import sleep


def exchange_spp_bytes(mac_addr, port):
    print(f'Connecting to bluetooth dev {mac_addr}, port {port}')

    s = socket.socket(socket.AF_BLUETOOTH, socket.SOCK_STREAM, socket.BTPROTO_RFCOMM)
    s.connect((mac_addr, port))

    while True:
        s.sendall(b"baba\n")
        print( s.recv(5) )
        sleep(0.5)


# Press the green button in the gutter to run the script.
if __name__ == '__main__':
    # Here we assume that we know what is port (BT channel)
    # Use SDP to identify which port is it
    # sdptool browse mac::address
    exchange_spp_bytes('REPLACE::WITH::BT::MAC:ADDRESS', 13)