StartServer listen failed error with UNET and WebGL

Hi everybody! I'm using Unity 5.3.4f1 and UNET to add networking to a WebGL game. I plan to eventually build my own matchmaking server so I'm not using the one supplied by Unity.
The problem is I have my NetworkManager object setup to listen using WebSockets.
When the game loads up in WebGL I try to Start a Server using NetworkManager.singleton.StartServer() I get the error message in the browser's debug console that "StartServer listen failed."
Can you not use WebSockets without Unity's...

StartServer listen failed error with UNET and WebGL