Joining multiple Multicast Streams

[Dex Nada]

Thank you very much. I currently use the SO_REUSEADDR flag. I will try
the SO_REUSEPORT as well - makes sense.

Thank again.

-DxN

On Thu, Dec 17, 2009 at 2:28 PM, Pieter de Goeje <pieter at degoeje.nl> wrote:
> On Thursday 17 December 2009 19:45:24 Dex Nada wrote:
>> Hi:
>>
>> I am writing an application that joins a multicast stream on a specific UDP
>> port. But when I run more than one instance of the same application, the
>> second instance complains that the port is already in use. For example if I
>> join stream 229.10.10.133:2000 on one instance and 229.10.10..134:2000 on
>> another instance, the second one fails to join - I can however join it if I
>> kill the first instance. I have compiled that application with SOCKET_REUSE
>> option, but I wonder if I need to enable/recompile-with any special
>> multicast kernel option for this to work. I do not have this problem when I
>> run this code on Linux (Ubuntu 9.10) but I really want to get this working
>> on FreeBSD.
>>
>> Thanks in advance.
>>
>> -DxN
>
> Try SO_REUSEPORT. The manpage (getsockopt(2)) specifically mentions multiple
> listeners for the same multicast stream. The following pseudo C seems to work
> fine:
>
> int reuseport = 1;
>
> memset(&addr, 0, sizeof(addr));
> addr.sin_family = AF_INET;
> addr.sin_addr.s_addr = htonl(INADDR_ANY);
> addr.sin_port = htons(port);
>
> mreq.imr_multiaddr.s_addr = maddr;
> mreq.imr_interface.s_addr = INADDR_ANY;
>
> int fd = socket(AF_INET, SOCK_DGRAM, 0);
> setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &reuseport, sizeof(reuseport));
> bind(fd, (struct sockaddr *)&addr, sizeof(addr));
> setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
> recvfrom(fd, ....);
>
> Good luck,
>
> Pieter de Goeje
>