Multiplayer in C3 is now "thing of interest" for me or how to say it. :)
I would like to ask about connection with Multiplayer plugin in C3, I read all these manuals as Ashley mentioned and yea it is difficult but thanks 
Ashley that it is very well described. I also tried chat example and experimenting with it.
- When I am on same WiFi network it works 100% like Lan.
- When I am on different WiFi there is sometimes problem then peer is disconnected so I guessing that host must be behind proxy, NAT or blocked some ports etc.. am I right? Simply host is not visible for peers.
- I also tried it via mobile data connection and it did not work. What is different in this case?
- What about publishing the multiplayer game (via C3 and their signaling server) on Google Play? Can there be a problem with the content (referring to the server) or requirements of additional permission on mobile?
- Lastly what about predefined Google play games API for multiplayer similiar to Google play games Leaderboards etc is it possible to implement it in C3 and may it be better?
Sorry for maybe strange questions but I am begginer in this area and I will be really glad for further explanation and tips for better understanding of whole thing. :))
I'm afraid you're delving into an area where few have traveled. I am working on a multiplayer game as well but mine will be purely web based and won't need to keep track of player movement. Thus, my ability to answer your questions is limited.
A lot of things can affect your connection. Something as common as Windows Firewall can deny a connection.
There will be additional requirements if you publish on Google Play. You're going to need to research their actual terms to figure out what you can and can't do. I do know that you can connect remotely to other devices. Plenty of apps do that.
As for leaderboards and handling real-time multiplayer connections, I suggest you look into websockets and creating your own websockets server as well as Ajax communications with web based servers. While the multiplayer plugin does work and will work for low latency connections it does have it's limitations. Since a game client acts as the host, the number of connections to that game client is going to be limited both by the power and the location of that device. If your host is in Germany on a 10 year old cell phone and all the other players are in Australia on desktop's, it's going to have issues.