> 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/server-api/server-api-4.0-de/erste-schritte/server-instance.md).

# Serverinstanz

## Erstellen eines Servers

Um einen Socket.IO-Server zu starten, erstellen Sie ein `Konfiguration`, setzen Sie die Bind-Adresse und den Port und starten Sie dann den Server.

```java
Configuration config = new Configuration();
config.setHostname("localhost");
config.setPort(9092);

SocketIOServer server = new SocketIOServer(config);
```

{% hint style="warning" %}
Bei der Verwendung von Frameworks wie **Spring Boot**, stellen Sie sicher, dass Sie importieren `com.socketio4j.socketio.Configuration` und nicht Framework-Klassen mit demselben Namen (zum Beispiel `org.springframework.context.annotation.Configuration`), um Importkonflikte zu vermeiden.
{% endhint %}

## Starten des Servers

{% tabs %}
{% tab title="Synchron" %}

```java
server.start()
```

{% endtab %}

{% tab title="Asynchron" %}

```java
server.startAsync().addListener(future -> {
            if (future.isSuccess()) {
                System.out.println("Server started on " + config.getPort());
            } else {
                System.out.println("Error " + future.cause().getLocalizedMessage());
            }
        });
```

{% endtab %}
{% endtabs %}

## Stoppen des Servers

Stoppen Sie den Server beim Herunterfahren immer sauber (gracefully).

```java
server.stop();
```

{% hint style="info" %}
socketio4j fügt nach dem Start des Servers einen Shutdown-Hook hinzu, der den Server in bestimmten Szenarien sauber beendet, aber nicht in allen. Es wird stets empfohlen, den Server explizit zu stoppen.
{% endhint %}

## Vollständiges Beispiel

{% code title="Server.java" %}

```java
import com.socketio4j.socketio.Configuration;
import com.socketio4j.socketio.SocketIOServer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class SocketIoServerMain {
    
    private static final Logger log = LoggerFactory.getLogger(SocketIoServerMain.class);
    
    public static void main(String[] args) throws Exception {
        // Konfiguration erstellen
        Configuration config = new Configuration();
        config.setHostname("localhost");
        config.setPort(9092);

        // Server erstellen
        SocketIOServer server = new SocketIOServer(config);
        
        server.addConnectListener(client -> {
            log.info("[/] connected -> " + client.getSessionId());
        });
        server.addDisconnectListener(client -> {
            log.info("[/] disconnected -> " + client.getSessionId());
        });
        
        server.addEventListener("hi", String.class, (client, data, ack) -> {
            // im Client auf "reply" hören
            log.info("received data : " + data);
            client.sendEvent("reply", "hello");
        });
        // Server starten
        server.start();
        log.info("Socket.IO server started on port 9092");

        // JVM am Leben halten
        Thread.currentThread().join();
    }
}

```

{% endcode %}

{% hint style="info" %}
Prüfen [Ereignisse](https://www.socketio4j.org/events/events-de/) für dokumentation zu ereignisbehandlung 
{% endhint %}

## Hinweise

* `hostname` ist optional. Wenn nicht gesetzt, bindet der Server an alle Schnittstellen (`0.0.0.0` / `::0`).
* `port` **muss** vor dem Starten des Servers gesetzt werden.
* Threading, Transports und andere erweiterte Optionen können über `Konfiguration` angepasst werden, bevor Sie `start() aufrufen`.


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