Firstly, AFAIK there isn't any released LFS_External library with these packets in it, so nobody can tell *exactly* how to send them.
Secondly, saving a list of all objects should be pretty easy.
Just handle them the same way as your Connections list.
<?php
List<AXMobjects> TrackObjects = new List<AXMobjects>();
?>
"AXMobjects" is whatever name the object structure is named in the library.
Then you simply add objects to the list when you received the object packet.
It's pretty hard to explain, unless we have the exact library