Internal PI system have exposed a WebService endpoint URL. There is firewall point lets say it <EXT_POINT:EXT_PORT>, which is accessible from outside the company premises, with http://<EXT_POINT:EXT_PORT>/<SomeService>, then request is forwarded to the PI. However, I believe on PI system, the reverse proxy should be configured. What I shall do is to setup the HTTP mapping:
<EXT_POINT:EXT_PORT> TO <PI_SYSTEM:PI_HTTP_PORT>
<SomeService> TO XISOAPAdapter/MessageServlet?channel=<PARTY>:<SENDER_COMP>:<CHANNEL>
Or am I missing something in the whole picture ..?