if(v == null) return;
    private void sendMessage() {        RspList rsp_list;        Message msg=new Message(null, null, "Hello world");        View v=channel.getView();        Vector members=new Vector(v.getMembers());        System.out.println("sending to " + members);        rsp_list=disp.castMessage(members, msg, GroupRequest.GET_ALL, 0);        System.out.println("responses:\n" + rsp_list);    }