> For the complete documentation index, see [llms.txt](https://www.socketio4j.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.socketio4j.org/example-projects/sample-projects/emergency-broadcast-app.md).
# Emergency broadcast app
## Server
```java
import com.socketio4j.socketio.Configuration;
import com.socketio4j.socketio.SocketIOServer;
import com.socketio4j.socketio.SocketIOClient;
public class EmergencyServer {
public static void main(String[] args) {
Configuration config = new Configuration();
config.setHostname("localhost");
config.setPort(9092);
SocketIOServer server = new SocketIOServer(config);
// Event: broadcast emergency messages
server.addEventListener("emergency", String.class,
(SocketIOClient client, String message, var ack) -> {
// print locally
log.info("EMERGENCY message received: {}", message);
// send to all clients
server.getBroadcastOperations().sendEvent("emergency", message);
});
server.start();
log.info("Emergency server started on :9092");
}
}
```
## Client
```html
Emergency Alert Client
🚨 Emergency Alert Listener
Status: Connecting...
```
---
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