To check that multicast is enabled
ifconfig -a
Needed interfaces should have "MULTICAST" indicated

Jini multicast groups:
JINI-ANOUNCEMENT(224.0.1.84)
JINI-REQUEST(224.0.1.85)

Routing tables and multicast groups
netstar -rn
netstat -gns
ip maddress list
route -n
If the destination 224.0.0.0 entry is not present you will need to enable multicast routing.

Default multicast group (replies from all multicast enabled hosts)
ping -s 224.0.0.1
ping -c 2 224.0.0.1

Snooping multicast packets
snoop -x 0 -d hme0 224.0.1.84
snoop -x 0 -d hme0 224.0.1.85

Adding the Multicast virtual network to the router table
route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0
route add 224.0.0.0 netmask 240.0.0.0 dev eth0
route add -net 224.0.0.0 -netmask 240.0.0.0 -interface en0 (BSD)

ip route add 224.0.0.0/4 dev eth0 (Linux)
Now, tell Linux to forward packets:
echo 1 > /proc/sys/net/ipv4/ip_forward

On Redhat systems, one can often configure this route statically via the network setup configuration tools.
Alternatively, try executing this line as part of a startup script in /etc/rc.d/*.

List multicast group to which the host is subscribed.
cat /proc/net/igmp

List multicast interfaces.
cat /proc/net/dev_mcast

All hosts configured for multicast will respond with their IP addresses
ping 224.0.0.1
All routers configured for multicast will respond
ping 224.0.0.2
All PIM routers configured for multicast will respond
ping 224.0.0.3
All DVMRP routers configured for multicast will respond
ping 224.0.0.4
All OSPF routers configured for multicast will respond
ping 224.0.0.5

IP sockets connections
netstat -f inet -n
What is on port 1023
lsof -i:1023