It aligns with what a lot of other apps are doing, e.g. tsplay.
Also added notes in docker to adjust network setting if wants to use
multicast in docker container.
Change-Id: I666a8979cc041c904f7ff8e3e022f800c0830d5d
This avoids interference caused when two sockets are bound to the
same port in different multicast groups.
Fixes#241
Change-Id: Iba1b3300e3850f1f268886b7a49f5a3315d95b80
fatpelt
KongQun Yang