Certain aspects and features provide generation or simulation of sensory data that would otherwise come from Internet-of-things (IoT) sensors in reproducible and controllable way. Thus, the response of a system to very large numbers of sensors can be tested without acquiring and deploying a very large number of sensors for test and development purposes. In some examples, a processing device coupled to a network interface identifies a stored function of time describing a locally sensed property for a simulated sensor. The locally sensed property corresponds to at least one event taking place in a virtual environment. The processing device can determine values of an input variable produced by the stored function of time. The values can be wrapped in a communication protocol to produce messages that are transmitted over the network interface.