Erm, actually 
it is possible via WebSockets (the demo looks broken currently though) but it only works on GitHub pages, making debugging almost impossible and needing external infrastructure or a finance API supporting WebSockets.
simmessages also exist but you need to write custom code that only runs in GitHub pages,. making debugging almost impossible and I’m unsure if you can send messages into the simulator.
So essentially it’s impossible to interact with the network, but it is always possible to simulate it in your game!