ExpressJs: doesn't work disconnection event using cloudflare

Hi, there!
I developed my backend server on localhost using express.js framework.
I’n using disconnection events. On localhost it works okay, but it doesn’t work on my dedicated server if cloudflare is used. If I disable proxy (enable DNS only mode) or connect to server IP directly it again works okay.
Why express.js can’t detect disconnection and call event when client connected throught cloudflare?
How can I solve it?
Thanks in advance!

Out of curiosity, are you using Rocket Loader from the Speed -> Optimization tab?