Ok, one last issue I found, I might go look at the source and see if the 3rd party library is exposing it and it just needs to be wrapped or if it isn’t there.
It looks like the client hears socket.emit but doesnt hear io.emit. Let me see if I can explain that better. On the javascript side there are events that are inside of your existing connection, and those are what I am considering socket.emit, then there are those that are server level that run in the game loop. They fire irregardless of your connection being present or not, though of course I suppress them when noone is connected 
Anyhow, awesome start! If I get time I will poke around at it and do a PR if it is something easy to fix but my C++ is limited at best
Edit: Sorry, just re-read the first message and noticed you stated this was very basic. Sorry for being silly