File system semantics, applied to the host/network interface of a wide area network, lead to a compact definition of communication service and provide a versatile framework for privacy and security. There is a symmetry in an interface language based upon files, flows and processes that seems to offer a lot of value from a rather simple foundation. In a network constructed on this principle, flows are named connections between processes, and virtual networks are named collections of flows. Access permissions are associated with the names of flows and networks. Pure clients are invisible and are not so easy to attack.