code for Device A (Advertiser)

gistfile1.txt

private void startAdvertising () {
            AdvertisingOptions advertisingOptions = new AdvertisingOptions.Builder().setStrategy(STRATEGY).build();
            Nearby.getConnectionsClient(BaseApplication.getInstance()
                    .getActivity()).startAdvertising("Device A", SERVICE_ID, new ConnectionLifecycleCallback() {
                @Override
                public void onConnectionInitiated(@NonNull String endPointId, @NonNull ConnectionInfo connectionInfo) {
                    Nearby.getConnectionsClient(BaseApplication.getInstance()
                            .getActivity().acceptConnection(endPointId, mPayloadCallback);
                }
                @Override
                public void onConnectionResult(@NonNull String endPointId, @NonNull ConnectionResolution connectionResolution) {
                    switch (connectionResolution.getStatus().getStatusCode()) {
                        case ConnectionsStatusCodes.STATUS_OK:
                            // We're connected! Can now start sending and receiving data.
                            strendPointId = endPointId;
                            sendPayLoad(strendPointId);
                            break;
                        case ConnectionsStatusCodes.STATUS_CONNECTION_REJECTED:
                            // The connection was rejected by one or both sides.
                            break;
                        case ConnectionsStatusCodes.STATUS_ERROR:
                            // The connection broke before it was able to be accepted.
                            break;
                        default:
                            // Unknown status code
                    }
                }
                @Override
                public void onDisconnected(@NonNull String s) {
                    strendPointId = null;
                }
            }, advertisingOptions);
}