Multicast UDP not working

I understand that your host, 192.168.2.7 is sending multicast packet to group 239.255.250.250 on port 9131

NOTE: I assume however that servers are listening on port 9131. you didn't provide any info on this.

From ifconfig output, I can see that MULTICAST is enabled and the tcpdump confirm this.

First make sure that the host running the servers (the one receiving the multicast packet) have joined the multicast group.

On each server host type :

netstat -gn

If you see your multicast address, it has joined the group. If not, then either something is wrong with your server program or possibly kernel settings.

If the server has joined the group but you don't see any packet incoming from client, then check on your router that you have enabled igmp ( your router must be igmp capable)

For example,on cisco router

enable
conf t
ip multicast-routing
For each interface involved.
int <NIC>
ip pim sparse-dense-mode

If igmp is enabled on router, look for debug features to track the packets.

On server side, start a packet capture :

tcpdump -i <NIC> host 239.255.250.250

If you don't see any packet coming in, then the multicast packet are not forwarded (assuming that

Then on client send a multicast packet (use the script in link below to troubleshoot)

NOTE: the UDP packet seems malformed so not sure if servers will be able to read it. You can use the script in link below to confirm whether or not the message in tcpdump are displaying as malformed or not ( they are not in my case)

Example of python code using multicast :

https://stackoverflow.com/questions/603852/multicast-in-python

NOTE: I used this script on a debian raspi ( not raspbian and server received packets through router - as setup above - fine)

Linux guide : http://stlinux.com/howto/network/short-guide

Cisco : http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_52_se/configuration/guide/3750scg/swmcast.html#wp1024278