Network Programming with Perl

Using Multicast

The remainder of this chapter shows you how to use multicasting in Perl applications.

Sending Multicast Messages

Sending a multicast message is as straighforward as creating a UDP socket and sending a message to the desired multicast address. Unlike broadcasting messages, to send multicast messages you don't have to get permission from the operating system first.

Recall from Chapter 20 that we were able to identify all the hosts on the local area subnet by pinging the broadcast address. We can use the same trick to identify multicast-capable hosts by sending a packet to the all-hosts group, 224.0.0.1:

 % ping 224.0.0.1 PING 224.0.0.1 (224.0.0.1): 56 data bytes 64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=1.0 ms 64 bytes from ...