pass source port to app server behind haproxy

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http://serverfault.com – I have a haproxy configuration run in http mode. I pass requests to backend java servers. I use forwardfor option to get client ip in backend server. I want to get source port in backend server but there isn't any option about this in haproxy conf. From maillist, i learnt, proxy protocol can be used for this. But i couldn't find any document or how-to about implementation of proxy protocol. Can i pass source port information to backend server only changing load balancer configuration? (HowTos)