GNU Smalltalk Library Reference: Sockets.MulticastSocketImpl-multicasting

ipMulticastIf: Answer the local device for a multicast socket (in the form of an address)
ipMulticastIf: interface: Set the local device for a multicast socket (in the form of an address, usually anyLocalAddress)
join: ipAddress: Join the multicast socket at the given address
leave: ipAddress: Leave the multicast socket at the given address
timeToLive: Answer the time to live of the datagrams sent through the receiver to a multicast socket.
timeToLive: ttl: Set the time to live of the datagrams sent through the receiver to a multicast socket.