OnIPMCastRead is a TIPMCastReadEvent property that represents the event handler signalled when a datapacket has been received on the socket descriptor for the multicast client. OnIPMCastRead allows the client to implement processing required to read and handle the datagram contents. 

Applications must assign a procedure to the TIPMCastReadEvent event handler to allow responding to the event notification. 

The event handler has arguments that include: 

TIPMCastReadEvent 

TIdSocketHandle