This section focuses on the message-passing mechanism for exchanging messages between VR-Forces applications and their simulation objects.

VR-Forces applications communicate all information through DIS PDUs or HLA RPR FOM objects and interactions. In addition to the standard protocol messages, VR-Forces sends messages that VR-Forces applications use to communicate with one another, such as scenario management, creating and deleting objects and simulation objects, and executing plans. In order to send these messages as part of DIS or RPR, these messages are encoded into VR-Forces specific records within Data or Radio Signal interactions, depending on the message.

There are two primary categories of VR-Forces messages.

Interface Messages are used to communicate from one VR-Forces application to another, such sending messages between the sim engine and the GUI.
Object Messages are used to communicate to or from a specific VR-Forces simulation object.

In either case there is a message class that acts as an envelope for a large, diverse selection of content classes. For Interface Messages it is DtSimInterfaceMessage. For Object Messages it is DtVrfObjectMessage. In order to send a VR-Forces message you must create an instance of the desired content. This content is then added to the appropriate message class and handed off to an interface class to send the message. The exact mechanism will depend on the type of message being sent.