Multicast Receive broke after upgrade to Red Hat 6.3
 

I have written some code that generates and receives multicast traffic, and it works fine in Ubuntu and Red Hat 5.5. However, when I upgraded Red Hat to 6.3, Multicast receive stopped working. Sending is still working fine, but receiving isn't.

The Multicast connection opens without errors, and the receive function call returns no errors. However, it is simply not receiving any data (it returns 0 bytes received). I know that the data is being sent, because I can receive it on another machine. But the Red Hat 6.3 machine isn't seeing it.

To write the code, I used the HawkNL networking library.

Any help is appreciated.

The problem was simply that the incoming multicast traffic was getting blocked by the Firewall. A colleague had to point this out to me. I didn't think of this, because it was sending the traffic fine (I could see the traffic from another machine), and I didn't think that a Firewall would, by default, block traffic from the local machine.