The Various network resources, including wireless access and multimedia devices, expected in ubiquitous computing environments, have limited geographical service areas and different attributes. This paper proposes adaptive terminal middleware that performs policy-based dynamic resource selection and host-based session management to hide session failures and resource changes from applications and a user. The middleware realizes a Virtual Socket, on top of real sockets, which employs a seamless session handoff mechanism for resource changes, and a resume and retransmission mechanism against disconnection of the wireless link. We implemented the middleware and a test application on top of it to evaluate the performance.