Several service discovery protocols are deployed in local-area networks allowing users to be informed about the services in their vicinities. However, these local-area discovery protocols are incapable of exposing the services to remote users. This paper proposes a P2P-based naming system to ensure wide-area service discovery for communications between devices and services often remotely located. The naming system enables the transparency of the discovery protocols by defining a unified naming scheme for services in wide-area environments. The naming system has a scalable P2P architecture and integrates a notification service which informs subscribers about the services and their mobility. As an application use case, this work extends UPnP, a local-area and plug-and-play service discovery protocol, to a wide-area service discovery system using the proposed P2P-based middleware.