How can I connect two devices together

Question

I'm new to reactive programming and this library and I'm trying to write an android app that will be able to send messages back and forth with other phones having the same app.

I've written a BleAdvertiser class which basically broadcasts the service UUID, I then use RxAndroidBle to identify other devices and attempt a connection. It would appear that I'm not actually making a connection, however, no errors are being thrown. What am I doing wrong?

On create I look for other phones with the same app. The Log statement that prints device name and MAC address is working as expected, I can see my test device. So I'm good there.

@Override
protected void onCreate(Bundle savedInstanceState) {
    ...

    Intent intent = new Intent(this, BluetoothLeService.class);
    startService(intent);

    BleAdvertiser bleAdvertiser = new BleAdvertiser(new AdvertisingPacket(new Date(System.currentTimeMillis())));

    Thread t = new Thread(bleAdvertiser);
    t.start();

    SERVICE = UUID.fromString("e12b9e62-5c03-4ca2-88a5-1034e494f4dc");
    CHARACTERISTIC = UUID.fromString("201274dd-04dc-4ce6-943c-a830df466b33");
    PUUID = ParcelUuid.fromString(SERVICE.toString());

    rxBleClient = RxBleClient.create(this);

    scanSubscription = rxBleClient.scanBleDevices(
            new ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_BALANCED).build(),
            new com.polidea.rxandroidble.scan.ScanFilter[]{new ScanFilter.Builder().setServiceUuid(PUUID).build()}
    )
        .subscribe(
            scanResult -> {
                //process new ble device.
                Log.d("Scan Result: ", scanResult.getBleDevice().getMacAddress() + " : " + scanResult.getBleDevice().getName() );
                ConnectToDevice(scanResult.getBleDevice());
            },
            throwable -> {
                Toast.makeText(this,throwable.getMessage(),Toast.LENGTH_LONG ).show();
            }
        );

    ...
}

So we try to connect:

private void ConnectToDevice(RxBleDevice device) {
    device.establishConnection(true)
        .flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(CHARACTERISTIC)
            .doOnNext(bytes-> {
                //process read data (convert to message? )
                try {

                    Toast.makeText(this,"stuff happened in what we think is read bytes.",Toast.LENGTH_SHORT).show();
                    ArrayList<TinCanMessage> receivedMessages = (ArrayList<TinCanMessage>) Serializer.deserialize(bytes);

                } catch (IOException e) {
                    e.printStackTrace();
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
            })
            .flatMap(bytes -> {
                Toast.makeText(this,"stuff happened in what we think is write bytes.",Toast.LENGTH_SHORT).show();
                try {
                    return rxBleConnection.createNewLongWriteBuilder()
                        .setCharacteristicUuid(CHARACTERISTIC)
                        .setBytes(Serializer.serialize(new TinCanMessage("New messages will go here.", "kyle")))
                        .build();
                } catch (IOException e) {
                     e.printStackTrace();
                }
                return null;
            })
        )
        .subscribe(
            bytes -> {
                //Written data
                //assign to fragment and update adapter?
                Toast.makeText(this, "stuff happened in the written data section", Toast.LENGTH_SHORT).show();
            },
            throwable -> {
                Toast.makeText(this, throwable.getMessage(), Toast.LENGTH_LONG);
            }
        );
}

All help is appreciated.

Update

The devices actually are connecting. I've verified this by printing out to the debugger. I thought that I had an issue because I was trying to verify the connection with toast messages which are not displaying. This was discovered via comments from Darkusz Seweryn, so I've accepted his answer. My question was built on faulty assumptions :P

Answer 1

The above code looks good in terms that it does not seem to have any flaws.

Two things you should try:

1. You should stop (unsubscribe from) the scan once you have scanned your device peripheral. You could do this automatically by adding .take(1) just before .subscribe() to .scanBleDevices().
2. You have used RxBleDevice.establishConnection(true). The autoConnect=true changes the behaviour of connection. With autoConnect=true the connection may be established even many minutes after the call. You could connecting with autoConnect=false which would connect (or fail) in just 30 seconds.