Paypal IPN callback - how to?

I'm using Paypal to make payments through my Rails app and I have IPN
setup so that when rails receives notification from Paypal, a record is
activated. This all works fine.

However, Paypal sends the notification multiple times. I think this is
because my controller is not notifying Paypal that it has received the
IPN call. I'm using ActiveMerchant.

I tested the script on http://www.eliteweaver.co.uk/testing/ipntest.php
(which is an IPN testing environment) and it said that my script was not
posting back to them.

Here is my code:

def notify
  # Create a notify object we must
  notify = Paypal::Notification.new(request.raw_post)

  if notify.acknowledge
    #record transaction details here...
    begin
      if notify.complete?
        #do some validation and then activate record
      else
         #Reason to be suspicious
      end

    rescue => e
      #There's a bug
      raise
    ensure
      #make sure we logged everything we must
    end
  end
  render :nothing => true
end

Does anyone know how to send the callback to Paypal to inform them that
I've received the IPN?

i a m a new one ruby on rails i want learn more things place help
me

That's what the notify.acknowledge should be doing.

However, I suspect that you need to somehow modify active merchant to
use the url for that testing site instead of paypal itself.