Wireless sensor networks (WSN) have been widely used in many applications, such as climate monitoring systems, fire detection, ocean activity monitoring, and smart cities. These networks can be homogeneous or heterogeneous, depending on the types of wireless devices used. WSNs play an important role monitoring and reporting environment information and collecting surrounding context to send it to a sink. The sink acts as a bridge between the WSN and the final user. The sink could be static, such as a base station or a gateway node or could be mobile such as a drone or an user carrying a smartphone. When the sink is mobile, the path to reach the sink from any node in the network becomes obsolete frequently. Then, the problem to address in this case is how to reach the sink, without drastically depleting the network energy resources. This paper focuses on networking protocols used to report events to a mobile sink and presents the state of the art in mechanisms used to report data and events to a mobile sink.