Since heroku server doesn't support websocket, does it mean if we run a node.js + io.socket app on it, expecting many concurrent users, some in effectiveness will happen when there are more users?
I was building a multiuser app and suddenly notice that heroku is using long poll instead of websockets. I couldn't see much delay in my prototype but I am worried, should i be building my app on a server that supports real websockets?
... should i be building my app on a server that supports real websockets?
Probably.
http://websocket.org/quantum.html, says "HTML5 Web Sockets can provide a 500:1 or—depending on the size of the HTTP headers—even a 1000:1 reduction in unnecessary HTTP header traffic and 3:1 reduction in latency."
Long polling is old and inefficient, and is slowly being replaced by sockets. They are supported by every server. Most of latest browsers have already added support too. Heroku will do that too, soon hopefully. You can continue with your prototype, maybe websocket support will be added before you finish it.
The advantages websocket are given here