What is the method to send multicast packet?

[zxg60481@mail1.sjtu.edu.cn (Zhu xg)]

Hello, all,
  An new agent is implemented, and I want to send the packet by multicast.
But I find different method to send a packet.

1.send(Packet* pkt, Handler* h)

2.target_->recv(Packet* pkt)

Is the method 1 used in connect oriented circumstance and the method 2 used
in connectless oriented ? When send a packet, should I set the destination
address? for example:
        hdrip->dst() = dst_;

In order to receive the multicast packets, should the nodes and the agent
join the group explicitly? for example:
    $ns at 0.0 "$n1 join-group $rcvr 0x8003"

  Any help is appreciated.

                  ZXG