If multicast does not work on Ubuntu

1. Check that you have a route to 224.0.0.0/4.
Substitute "eth0" with your interface.
Run
# sudo ip route
and check if you have:
224.0.0.0/4 dev eth0  scope link
If not, then add to /etc/network/interfaces:
up ip route add 224.0.0.0/4 dev eth0
Like this:
auto eth0
iface eth0 inet static
        address 192.168.1.2
        netmask 255.255.255.0
        up ip route add 224.0.0.0/4 dev eth0

2. At the end of /etc/sysctl.conf add:
net.ipv4.conf.all.rp_filter=0
net.ipv4.conf.default.rp_filter=0
net.ipv4.conf.all.mc_forwarding=1
net.ipv4.conf.default.mc_forwarding=1

3. Reboot.