I have the following function to send data over bluetooth to a bluetooth serial monitor running on my laptop.

private fun sendData(mSocket: BluetoothSocket?, data: String) { //mSocket: "XX:XX:XX:XX:6E:D0" data hello world!
        if (mSocket == null) {
            return
        }

        val outputStream: OutputStream
        try {
            outputStream = mSocket.outputStream //mSocket: "XX:XX:XX:XX:6E:D0"
        } catch (e: IOException) {
            Log.d("Outputstream", "Error occurred when creating output stream: ${e.message}")
            return
        }

        try {
            val dataWithNewline = "$datan"
            outputStream.write(dataWithNewline.toByteArray())
            outputStream.flush()
            Log.d("sendData", "Data sent: $data")
        } catch (e: IOException) {
            Log.d("sendData", "Error occurred when sending data: ${e.message}")
        }
    }

The bluetooth socket is created and connected succesfully, however when I try to send data, nothing happens. No IOException is thrown either. In Logcat I see “Data sent: hellow world!” indicating the data got sent over. On the receiving end however I dont see anything. In the comments in my code I wrote down some variable values when I put a breakpoint at the end of the function. Why does my MAC address show up truncated: “XX:XX:XX:XX:6E:D0”? After inspecting mSocket I do see the full MAC address under the mAddress variable.

This is the function to connect to my device:

fun connectOBDDevice(deviceItem: BluetoothDeviceItem) {
        val mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
        val device: BluetoothDevice? = mBluetoothAdapter.getRemoteDevice(deviceItem.address)
        try {
            val createInsecureRfcommSocket = BluetoothDevice::class.java.getMethod("createInsecureRfcommSocket", Int::class.javaPrimitiveType)
            mSocket = createInsecureRfcommSocket.invoke(device, 1) as BluetoothSocket
        } catch (e: Exception) {
            // e.printStackTrace();
            Log.d("connectOBDDevice", "createInsecureRfcommSocket failed")
        }
        if(mSocket != null)
        {
            if (ContextCompat.checkSelfPermission(
                    requireContext(),
                    Manifest.permission.BLUETOOTH_CONNECT
                ) == PackageManager.PERMISSION_GRANTED
            ) {
                try {
                    mSocket.connect()
                    val receiveThread = BluetoothReceiveThread(mSocket)
                    receiveThread.start()
                    Toast.makeText(context, "Device connected successfully!", Toast.LENGTH_SHORT).show()
                }
                catch (e: IOException)
                {
                    Toast.makeText(context, "Connection Failed", Toast.LENGTH_SHORT).show()
                }
            }
        }
    }

Any help would be appreciated!

I tried using the “Serial Bluetooth” app on my phone to test the connection and while using this everything works fine.