What exactly does handleParkingUpdate() do?

I am trying to implement a VANET model for smart parking simulations. Trying to fully understand the TraCIDemo11pp.cc and files relevant to it and its proving quite difficult to get my head around the general structure of each module and the communications between them despite understanding the TicToc tutorial.

I understand how SUMO and OMNETPP are run in parallel, TraCIScenarioManager from OMNETPP communicates with the TraCI server in order to exchange information to SUMO etc. But I'm finding it hard to get my head around how the TraCIDemoApp is utilised.

The question is quite specific, but hoping an answer to it would let me figure out the rest. Any help would be appreciated!

Thanks, Wesley

Veins comes with a very small demo example in the city of Erlangen:

Vehicles start at the parking lot of the university and drive to a location off-sight. After some time the first vehicle (node[0]) emulates an accident and stops driving. Therefore, it broadcasts this information which gets re-distributed via the RSU to all other vehicles in range. They, in turn, try to use an alternative route to their destination while re-broadcasting the information about the accident. Thus, newly spawned vehicles also get informed and immediately try to choose a different route to the destination.

All of this (i.e. accident, broadcasting, switching route) is implemented in the TraCIDemo* files which represent a VANET application running in a car or RSU utilizing the NIC (i.e. PHY & MAC) to do communication. See what policy is based vehicle rerouting in case of accident? for more information.

handleParkingUpdate() is used to react to a vehicle having switched it's state from driving to parking or vice versa. Depending on the current state and whether parked cars should be allowed to communicate in the simulation this method registers the vehicle's NIC module at the BaseConnectionManager which is involved in handling the actual wireless communication. For more details see this module or follow a packet from one application layer to another (i.e. twice through the networking stack and the wireless transmission).