> Markdown version of [Hilla Services](https://vaadin.com/docs/v24/building-apps/deep-dives/presentation-layer/server-push/reactive-browser-callable-services). Section index: [llms.txt](https://vaadin.com/docs/v24/building-apps/llms.txt)

# Reactive Browser Callable Services Hilla

When building a user interface with Vaadin Hilla, you would use reactive browser callable services to push messages from the server to the browser. A reactive service is a service that returns a `Flux` from [Reactor](https://projectreactor.io/).

Here is an example of a browser callable service that emits the current date and time every second:

```java
@BrowserCallable
public class TimeService {

    @AnonymousAllowed
    public Flux<@Nonnull String> getClock() {
        return Flux.interval(Duration.ofSeconds(1)) // (1)
                .onBackpressureDrop() // (2)
                .map(_interval -> Instant.now().toString()); // (3)
    }
}
```

1. Emit a new message every second.

2. Drop any messages that for some reason can’t be sent to the client in time.

3. Output the current date and time as a string.

Hilla generates the necessary TypeScript types to subscribe to this service from the browser.

For more information about updating the UI using a reactive service, see the [Reactive Streams](https://vaadin.com/docs/v24/building-apps/deep-dives/presentation-layer/server-push/reactive.md) documentation page.