DEF_IMP_THREADEDEVENT is a constant value that represents the default value used the
TIdIPMCastClient.ThreadedEvent property. DEF_IMP_THREADEDEVENT is assigned to the property in the constructor for a
TIdIPMCastClient instance, and indicates if the
TIdIPMCastListenerThread for the client should use it's IPMCastRead method independent of the main VCL thread during startup.