Socket.io in reconnecting loop when running in Amazon EC2

I am having a problem with socket.io (websocket) when running in EC2. I don't have any http proxy or loadbalancer installed infront of the node instance. Same code works fine when running in local environment but keep reconnecting in EC2. Also even in the EC2 instance xhr-polling works fine.

Following is socket.io debug log output when transport is set to websocket and xhr-polling.

debug - discarding transport
debug - authorized
info  - handshake authorized aoiP_6qFnqiqEC3r2-0N
debug - setting request GET /socket.io/1/websocket/aoiP_6qFnqiqEC3r2-0N
debug - set heartbeat interval for client aoiP_6qFnqiqEC3r2-0N
debug - client authorized for 
debug - websocket writing 1::

warn  - websocket parser error: reserved fields must be empty
info  - transport end (undefined)
debug - set close timeout for client NxkBCtJqwOscfHzE0xba
debug - cleared close timeout for client NxkBCtJqwOscfHzE0xba
debug - cleared heartbeat interval for client NxkBCtJqwOscfHzE0xba