Add the option to bind to a specific address

src/defaultsettings.cpp

@@ -175,6 +175,7 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("workaround_window_size","5");
 	settings->setDefault("max_packets_per_iteration","1024");
 	settings->setDefault("port", "30000");
+	settings->setDefault("bind_address","");
 	settings->setDefault("default_game", "minetest");
 	settings->setDefault("motd", "");
 	settings->setDefault("max_users", "15");