How to test asynchronous services ?

I’m interested by testing asynchronous services with soapUI.
I would like to have soapUI behaves as a server to receive the request from system A, then behaves as a client to send the reply to system B. (Obviously data received from system A are used to compute data sent to system B and so take some seconds or minutes to do that).

The title of this page : Testing Asynchronous Services looks promising but the page is empty

Please, can someone give me some detailled instructions to do that?

Thanks.