The @{rednet_message} event is fired when a message is sent over Rednet.
This event is usually handled by @{rednet.receive}, but it can also be pulled manually.
@{rednet_message} events are sent by @{rednet.run} in the top-level coroutine in response to @{modem_message} events. A @{rednet_message} event is always preceded by a @{modem_message} event. They are generated inside CraftOS rather than being sent by the ComputerCraft machine.