In the future, robots will use various robot H/W platforms and their services will be composed of S/W components. Accordingly, it needs a robot S/W platform that provides standardized components and interfaces for fast robot development. OPRoS(Open Software Platform for Robotics Services) is a robot S/W platform that provides standardized components and interfaces. It uses the UPnP(Universal Plug and Play) as communication middleware. The UPnP is designed to bring easy-to-use, flexible, and standards-based connectivity to ad-hoc or unmanaged networks. We use UPnP eventing for push-style data transfer. But, the UPnP eventing has an inefficient factor for this. In this paper, we explain the reason and propose a single event mechanism to overcome the inefficiency.