I want to know how router schedule Multicast listeners. For example, if 2 hosts are connected to a router, and they want to listen same multicast server, which one of the 2 gets the multicast packet first?
They will receive the packet at the same time (assuming the distance to both machines is the same).
The router doesn't send two unicast packets to two separate machines, sending one before the other. Instead, it sends a single multicast packets with a special multicast MAC address and a multicast IP address. All machines (and routers) on the same LAN that listen to the same multicast group will receive that packet.