only redirect port if iptables is available

src/de/tudarmstadt/informatik/hostage/net/MyServerSocketFactory.java

@@ -37,7 +37,7 @@ public class MyServerSocketFactory extends ServerSocketFactory {
 				} catch (IllegalAccessException e) {
 				} catch (IllegalArgumentException e) {
 				}
-			} else { // use ip tables
+			} else if (Device.isPortRedirectionAvailable()) { // use ip tables
 				int redirectedPort = HelperUtils.getRedirectedPort(port);
 				socket = new ServerSocket();
 				socket.setReuseAddress(true);