According to the streaming schedule for this week, tomorrow's Devils-Flyers preseason game will be streaming at 7:10 PM EST at WFAN.com. It will not be on WFAN, the radio station; so if you tune in to 660 AM, you'll get the Mets game instead.
As far as I know, the game's not televised locally for the Devils, so this is your legal way to follow the game. Failing that, just show up at the Rock and, well, see it live.
Also: Expect a late afternoon preview for tomorrow's game.