In wireless sensor networks, there is usually a sink which gathers data from the battery-powered sensor nodes. As sensor nodes around the sink consume their energy faster than the other nodes, several sinks have to be deployed to increase the network lifetime. In this paper, we motivate the need of anycast communications in wireless networks, where all the sinks are identical and can gather data from any source. To reduce interference and congestion areas on the wireless medium, the path from a source to a sink has to be distant from the path connecting another source to another sink. We show that determining distant paths from sources to sinks is an NP-hard problem, and we propose a linear formulation in order to obtain optimal solutions. Then, we propose a sink selection and routing protocol called S4 and based on realistic assumptions and we evaluate it through simulations. Finally, we conclude that anycast routing protocols in wireless sensor networks should not compute paths independently for each source, but rather consider all the sources simultaneously.