public class BasicApnsConnection {

    private final Socket apnsSocket;
    private final DataInputStream apnsIn;
    private final OutputStream apnsOut;
    private final ExecutorService apnsInExecutor;
    private final Future<ApnsException> inputstreamTask;

    BasicApnsConnection(SocketFactory socketFactory, String host, int port)
            throws UnknownHostException, IOException {
        apnsSocket = socketFactory.createSocket();
        apnsSocket.setKeepAlive(true); // I tried to add this line, but it didn't work
        apnsSocket.connect(new InetSocketAddress(host, port));

        apnsIn = new DataInputStream(this.apnsSocket.getInputStream());
        apnsOut = this.apnsSocket.getOutputStream();
        apnsInExecutor = Executors.newSingleThreadExecutor();

        inputstreamTask = apnsInExecutor.submit(new InputstreamHandler());
    }

    public synchronized void push(ApnsNotification notification)
            throws ApnsException {
        if (notification == null) {
            throw new IllegalArgumentException("notification is null");
        }

        checkIfExceptionOccurred();

        ByteArrayOutputStream bytesBuffer = new ByteArrayOutputStream();
        notification.serialize(bytesBuffer);
        byte[] dataBytes = bytesBuffer.toByteArray();
        try {
            apnsOut.write(dataBytes);
            apnsOut.flush();
        } catch (IOException ex) {
            throw new ApnsNetworkException("IOException occurred during " +
                    "pushing a notification to the APNS server", ex);
        }
    }

    private void checkIfExceptionOccurred() throws ApnsException {
        try {
            if (inputstreamTask.isDone()) {
                throw inputstreamTask.get();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }

    private class InputstreamHandler implements Callable<ApnsException> {

        @Override
        public ApnsException call() throws IOException, ApnsException {
            byte[] errorResponse = new byte[6];
            try {
                apnsIn.readFully(errorResponse);

                byte command = errorResponse[0];
                if (ApnsCommand.ERROR_COMMAND.getCode() != command) {
                    return new ApnsException(String.format(
                            "Unknwon command: %b from the APNS error response",
                            command));
                }

                byte status = errorResponse[1];
                int identifier = SerializationUtils.toInt(errorResponse, 2);
                if (status == ErrorStatus.NO_ERRORS) {
                    return new ApnsException("no errors"); // never reaches
                } else if (status > ErrorStatus.NO_ERRORS &&
                        status <= ErrorStatus.INVALID_TOKEN) {
                    return new ApnsMalformedException(status, identifier);
                } else if (status == ErrorStatus.SHUTDOWN) {
                    return new ApnsShutdownException(identifier);
                } else {
                    return new ApnsException("Unknown");
                }
            } catch (IOException ex) {
                return new ApnsNetworkException(
                        "IOException occurred while pushing a notification",
                        ex);
            } catch (Exception ex) {
                return new ApnsException("Unknown exception", ex);
            }
        }
    }
}