To use VLC to browse UPnP servers like MediaTomb, you must turn on the Universal Plug n Play Services Discovery module. To do so, open VLC, go to Tools and Preferences, select All under Show settings, open Playlist, select Services discovery, and check Universal Plug'n'Play. Then, click Save and exit VLC.
Now you can reopen VLC. To browse UPnP servers, click the Playlist button, open Local Network in the left pane, and choose Universal Plug'n'Play.
Asset is a UPnP (DLNA compatible) audio server, UPnP is a method of sharing media content between devices. Typically audio files are stored on a computer, server or NAS, multiple audio devices around the home network can play audio from the UPnP server (devices such as Linn DS, XBox 360, PS3, etc).