Updated 'MdgaServer' class.

Updated the 'MdgaServer' class by adding the 'shutdown' message to it.

Projekte/mdga/client/src/main/java/pp/mdga/client/server/MdgaServer.java

@@ -296,4 +296,21 @@ public void broadcast(ServerMessage message) {
     public void disconnectClient(int id) {
         this.myServer.getConnection(id).close("");
     }
+
+    /**
+     * This method will be used to shut down the server.
+     * It will iterate threw all connections of myServer attribute and check if they are equal to null. If not they will
+     * be closed. After that the myServer attribute will be closed and this program will be exited with the exit code 0.
+     */
+    @Override
+    public void shutdown() {
+        for (HostedConnection client : this.myServer.getConnections()) {
+            if (client != null) {
+                client.close("Host closed the server.");
+            }
+        }
+
+        this.myServer.close();
+        this.exit(0);
+    }
 }