CODEWITHSUNDEEP
linuxnetwork-programmingmulticastmulticastsocket
Dima
Dima

Reputation: 1311

receive multicast from specific network interface on Linux

I'm trying to receive a multicast data from specific network interface on CentOS 5.5

sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(1234);
addr.sin_addr.s_addr = htonl(INADDR_ANY);
bind(sd, (sockaddr*)&addr, sizeof(sockaddr_in));
setsockopt(sd, SOL_SOCKET, SO_BINDTODEVICE, "eth0", 5);

But I'm receiving packets from all interfaces.

What wrong?

Upvotes: 5

Views: 4287

Answers (1)

nos
nos

Reputation: 229108

First, check if any of your calls fail, socket,bind,setsockopt in this case. Printing an error message with the perror() function will help you diagnose problems.

However, for receiving multicast datagrams you might need to specify the ip address of the interface when you join a multicast group using the IP_ADD_MEMBERSHIP socket option Something like 

  setsockopt (sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq));

where the mreq struct is

struct ip_mreq
{
        struct in_addr imr_multiaddr;   /* IP multicast address of group */
        struct in_addr imr_interface;   /* local IP address of interface */
};

More info here.

Upvotes: 6

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