Move free port obtaining to util class

src/main/java/net/minestom/server/extras/lan/OpenToLAN.java

@@ -3,6 +3,7 @@ package net.minestom.server.extras.lan;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.event.server.ServerListPingEvent;
 import net.minestom.server.timer.Task;
+import net.minestom.server.utils.NetworkUtils;
 import net.minestom.server.utils.time.Cooldown;
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
@@ -57,9 +58,7 @@ public class OpenToLAN {
 
             if (port == 0) {
                 try {
-                    final ServerSocket socket = new ServerSocket(0);
+                    port = NetworkUtils.getFreePort();
-                    port = socket.getLocalPort();
-                    socket.close();
                 } catch (IOException e) {
                     LOGGER.warn("Could not find an open port!", e);
                     return false;

src/main/java/net/minestom/server/utils/NetworkUtils.java

@@ -0,0 +1,29 @@
+package net.minestom.server.utils;
+
+import java.io.IOException;
+import java.net.ServerSocket;
+
+/**
+ * Network related utilities.
+ */
+public class NetworkUtils {
+
+    private NetworkUtils() { }
+
+    /**
+     * Gets a free port.
+     *
+     * @return the port
+     * @throws IOException if a port could not be found
+     */
+    public static int getFreePort() throws IOException {
+        int port;
+
+        final ServerSocket socket = new ServerSocket(0);
+        port = socket.getLocalPort();
+
+        socket.close();
+
+        return port;
+    }
+}