Receiving multiple multicast feeds on the same port - C, Linux

Question

I have an application that is receiving data from multiple multicast sources on the same port. I am able to receive the data. However, I am trying to account for statistics

Answer 1

You can separate the multicast streams by looking at the destination IP addresses of the received packets (which will always be the multicast addresses). It is somewhat involved to do this:

Bind to INADDR_ANY and set the IP_PKTINFO socket option. You then have to use recvmsg() to receive your multicast UDP packets and to scan for the IP_PKTINFO control message. This gives you some side band information of the received UDP packet:

struct in_pktinfo {
    unsigned int   ipi_ifindex;  /* Interface index */
    struct in_addr ipi_spec_dst; /* Local address */
    struct in_addr ipi_addr;     /* Header Destination address */
};

Look at ipi_addr: This will be the multicast address of the UDP packet you just received. You can now handle the received packets specific for each multicast stream (multicast address) you are receiving.