[Boost-users] Multicast using Asio

Hi, I'm working on a rudimentary pub/sub mechanism using Asio, with the requirement that the publisher be notified when a new subscriber appears. Using multicast, this would correspond to a subscriber joining the multicast group. But it appears there's no way for the publisher to know this, correct? If so, is the only alternative to dedicate a socket to each pub/sub pair? Thanks, Vince