The following example uses a RoomListSnapshot to retrieve a one-time list of rooms on tryunion.com (Union's public testing server):
Union "snapshots" provide a traditional request/response mechanism for retrieving data on demand from Union Server. Snapshot data is not automatically synchronized with Union Server; instead snapshots are updated only when Orbiter's updateSnapshot() method is called (i.e., via "client pull" rather than "server push").
For an automatically synchronized list of rooms on Union Server, use RoomManager's watchForRooms() method (see lobby example) instead of RoomListSnapshot.
Here is the code for the preceding example. Click the "+" button to edit it live on JSFiddle.