Cool stuff, nice of you to share but whats the reasoning for another server? Why not the server be a proper modern rest client like retrofit and okhttpclient, and push events through websockets (just like push notifications), retrofit comes with okhttpclient 3.6 which include a websocket layer, also the .net part looks fairly limited since the knowledge base of asp related stuff is really small compared to smth like spring framework with a rest consuming front end like anguarjs, 2 birds with 1 stone. ^^
So my reasoning, you have a web app, let the web app be the resource server, while the server be a slave client. This way you limit network overhead and don't need to secure a random port out of the blue, also you have access to SSL/TLS :)
Still tho all this is really progressing the knowledge base of l2j and .net web apps, i find it quite interesting, GL! Hope to see this thing go off big :D