This paper addresses flow control and resource allocation problem for heterogeneous wireless sensor networks which consist of diverse sensor types and applications. The performance of these applications, either elastic data collecting or real-time monitoring, is modelled as a utility function of the sensor source rate. The traditional optimal flow control approach, which requires the utility function to be strictly concave, is no longer applicable because of realtime applications involved. Therefore, we propose a new utility-based flow control framework that is able to allocate the resources (wireless channel usage and sensor node energy) efficiently and guarantee the application performance in a utility proportional or max-min fair manner. Furthermore, the optimization and convergence of the algorithm is examined in the paper as well.