[asio] Using struct ip_mreqn to joing multicast group

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[asio] Using struct ip_mreqn to joing multicast group

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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

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Fon: +49 531 38 701 716            38124 Braunschweig
Fax: +49 531 38 701 88


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