I'm running Ubuntu 11.10. I have a local application that is trying to receive multicast UDP streams via an OpenVPN tunnel. I have network connectivity to the remote host that is generating the multicast data and can access that host properly. In addition, if I fire up Wireshark on my local machine, it is able to see the UDP packets coming through with the designated multicast destination addresses. However, my client application isn't indicating that it has received any data, so I'm trying to figure out the reason why.
Is there a simple tool that I can use at the command line to verify that the multicast traffic is being passed through to the user level? I'm wondering if there is something between Wireshark and userland that is filtering the packets for some reason. I've also tried using
tcpdump as follows:
sudo tcpdump -n -i tap0 -s 1536 udp
When I run this command, I also see messages fly by showing reception of the packets as I would expect. I'm not too familiar with the innards of
tcpdump, however; I'm not sure if it's also peeking down further under the hood than a typical user application would. Any suggestions?