You can use Bluetooth LE Advertising to broadcast data packages to all nearby devices without having to establish a connection first. Bear in mind that there’s a strict limit of 31 bytes of advertisement data. Advertising your device is also the first step towards letting other users connect to you.

Since not all devices support Bluetooth LE Advertising, the first step is to check that your device has all the necessary requirements to support it. Afterwards, you can initialize a BluetoothLeAdvertiser object and with it, you can start advertising operations:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && bluetoothAdapter.isMultipleAdvertisementSupported())
{
    BluetoothLeAdvertiser advertiser = bluetoothAdapter.getBluetoothLeAdvertiser();

    AdvertiseData.Builder dataBuilder = new AdvertiseData.Builder();
   //Define a service UUID according to your needs                
   dataBuilder.addServiceUuid(SERVICE_UUID);
    dataBuilder.setIncludeDeviceName(true);

     AdvertiseSettings.Builder settingsBuilder = new AdvertiseSettings.Builder();
     settingsBuilder.setAdvertiseMode(AdvertiseSettings.ADVERTISE_MODE_LOW_POWER);
     settingsBuilder.setTimeout(0);

     //Use the connectable flag if you intend on opening a Gatt Server
     //to allow remote connections to your device.
     settingsBuilder.setConnectable(true);

    AdvertiseCallback advertiseCallback=new AdvertiseCallback() {
    @Override
    public void onStartSuccess(AdvertiseSettings settingsInEffect) {
        super.onStartSuccess(settingsInEffect);
        Log.i(TAG, "onStartSuccess: ");
    }

    @Override
    public void onStartFailure(int errorCode) {
        super.onStartFailure(errorCode);
        Log.e(TAG, "onStartFailure: "+errorCode );
    }
  };
advertising.startAdvertising(settingsBuilder.build(),dataBuilder.build(),advertiseCallback);
}