Zitat von
http://en.wikipedia.org/wiki/IP_multicast:
An
IP multicast group address is used by sources and the receivers to send and receive multicast messages. Sources use the group address as the
IP destination address in their data packets. Receivers use this group address to inform the network that they are interested in receiving packets sent to that group. For example, if some content is associated with group 239.1.1.1, the source will send data packets destined to 239.1.1.1. Receivers for that content will inform the network that they are interested in receiving data packets sent to the group 239.1.1.1. The receiver joins 239.1.1.1. The protocol typically used by receivers to join a group is called the Internet Group Management Protocol (IGMP).
Wen ich das richtig interpreriere muss der Empfänger dieser Multcastgruppe beitreten - Ansonsten erreichen ihn die Packete nicht.
Multicastgruppen werden
IMHO auf dem Router verwaltete.
Ein UDPserver muss dann nur noch auf seine
IP-Adresse lauschen, denn der Router repliziert den Multicasttraffic auf diese Adresse.
Nachtrag 1:
Quelle:
http://www.tcpipguide.com/free/t_IPM...dressing-2.htm
Tabelle 49: 224.0.0.1 -> sendet traffic an alle devices im Subnetz
Grüße
Klaus