In this paper, the problems of distributed wireless sensor networks in heterogeneous interconnection and resource management are studied, and the necessity of combining software-defined networking with wireless sensor networks is analyzed. After summarizing a large number of software-defined wireless sensor networks architectures, a general architecture, in which the application plane, control plane and data plane can be described in detail, is proposed. In addition, the existing challenges and key technologies are laid out from four aspects:heterogeneous interconnection, resource management, reliable control and network security. Furthermore, advantages and prospects of the software-defined wireless sensor networks are illustrated via case comparison, and some future research work is outlined.