The computing and networking capacities of today's wireless portable devices allow for pervasive services, which are seamlessly networked. Indeed, wireless handheld devices now embed the necessary resources to act as both service clients and providers. However, the seamless networking of services remains challenged by the inherent mobility and resource constraints of devices, which make services a priori highly volatile. This paper discusses the design, implementation and experimentation of the ubiSOAP service-oriented middleware, which leverages wireless networking capacities to effectively enable the seamless networking of services. ubiSOAP specifically defines a layered communication middleware that underlies standard SOAP-based middleware, hence supporting legacy services while exploiting nowadays pervasive connectivity.