How the IP address is recognized in the Internet in multicast? -

How the IP address is recognized in the Internet in multicast? -

i referring "broadcasting multiple recipients" oracle java tutorial:

both server , client utilize grouping identifier identify belong same group. grouping id duplicate in net (and goolged , said grouping identifier not need unique)

then how come client on other side of net can know belongs same grouping of server? give me links describe process?

if server mutlicasts sound streams, server b multicasts video streams. server uses grouping id 203.0.113.0:4446 server b happens uses grouping id 203.0.113.0:4446. how come clients in net knows differences? since server not know existence of server b @ all, not know how take unique grouping id, uniqueness in ip address.

it seems cross articles, talking adding mac address. in oracle java tutorial, coding client not mention mac address @ all.

i don't know mean 'reorganized' in title, client doesn't 'know belongs same grouping [as] server'. knows belongs grouping defined ip address. if there multiple hosts sending ip address receive of them.

multicast