[Boost-users] [asio] Using struct ip_mreqn to joing multicast group

Subject: [Boost-users] [asio] Using struct ip_mreqn to joing multicast group
From: Klebsch, Mario (Mario.Klebsch_at_[hidden])
Date: 2018-04-20 10:04:04

Hi,

I need to receive multicasts on multiple interfaces and handle them differently, depending on the network interface they arrived on.

For each network interface, I create an UDP socket and I use

Socket.set_option(boost::asio::ip::multicast::join_group(MCastReqAddr.to_v4(), LocalAddr.to_v4() ), ec);

to join the multicast group. LocalAddr is the local IPv4 address of the interface. Unfortunately, I receive each incoming multicast message on each socket.

I found, that boost::asio::ip::multicast::join_group uses struct ip_mreq, where the multicast address and the local address can be specified.

On linux the man page on IP_ADD_MEMBERSHIP tells to use struct ip_mreqn. This structure had an additional member imr_ifindex. The documentation is not very clear about the difference between imr_address and imr_ifindex. So, I want to try it out and wonder, whether boost::asio supports using struct ip_mreqn for IP_ADD_MEMBERSHIP.

If not, does anybody know, how to write my own class  to be used with Socket.set_option?

73, Mario
--
Mario Klebsch                      Actia I+ME GmbH
Mario.klebsch_at_[hidden]<mailto:Mario.klebsch_at_[hidden]>         Dresdenstrasse 17/18
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