[PHP] 멀티캐스트 소켓 프로그래밍(simple)

http://calamitycoder.com/PHP/PHP-Multicast-Client-Server-Example.php

http://ntrg.cs.tcd.ie/undergrad/4ba2/multicast/antony/example.html
http://www.iana.org/assignments/multicast-addresses/multicast-addres
ses.xhtml

http://unabated.tistory.com/entry/Multicast-Address-%EB%A9%80%ED%8B%
B0%EC%BA%90%EC%8A%A4%ED%8A%B8-%EC%A3%BC%EC%86%8C

[iptables]
https://www.centos.org/forums/viewtopic.php?t=8286

sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=0

iptables -A INPUT -s 224.0.0.0/4 -j ACCEPT
iptables -A INPUT -d 224.0.0.0/4 -j ACCEPT
iptables -A INPUT -s 240.0.0.0/5 -j ACCEPT
iptables -A INPUT -m pkttype --pkt-type multicast -j ACCEPT
iptables -A INPUT -m pkttype --pkt-type broadcast -j ACCEPT