原理：
构造igmp包，然后使用libpcap抓包，获取组播地址和端口。
to compile it:
g++ -g -o iptvscanner iptvscanner.cpp -lpcap
usage:
./iptvscanner 239.3.1.1 239.3.1.254
todo:
save m3u playlist
if you don't scan any channel,try to increase timeout by changeing usleep(150000) to sleep(1) or sleep(2)