public List<String> listMembers(String group, UserToken token) {
        try {
            // send the message to the server:
            Message m = new Message(group, ServerAction.LIST_MEM, token, messageCounter++);
            //output.writeObject(m);
            output.writeObject(securityManager.encryptMessage(m));

            // get a message back, and see if it succeeded.
            //m = (Message) input.readObject();
            m = securityManager.decryptMessage((SealedObject) input.readObject());
            if (!m.success) {
                // if it did not succeed, say why:
                System.out.println(m.message);
                return null;
            }

            // split the message by commas:
            List<String> members = new ArrayList<String>();
            String[] mems = m.message.split(",+");
            for (String s : mems) {
                members.add(s);
            }
            return members;

        } catch (Exception e) {
            System.err.println(e);
            return null;
        }
    }