The how do I FAQ has a few items listed in the "multiplayer" section as this question already has been asked a few times.
It's possible but requires time and coding skills.
You can use the websocket custom plugin to handle the communication part of the client (the c2 app) and connect it to your webserver.
The websocket might not be up to date I haven't really followed this in a while.
Just check the items in the how do I and have a search for the keyword "Multiplayer" in the C2 and "how do I" forums, you should be able to find more.
Some tests and teasers topics have been done but no working solution has been yet been made public.