There looks to be an error returned here from the `portMapper.Unmap` method because the first ip/port is successfully released but the second ip/port fails because it is not found in the map.  

The portMapper uses ints as the key in it's dict, this should probably be changed to use a string with the format of `ip:port`.  This struct is not serialized to disk and should be safe to change the format for the keys.