Oops almost forgot: Instructions to setup PRPC on VMware and local Tomcat to use as test environment:

There is a lot of detailed documentation on PDN and in various Academy courses on Pega Mashup/IAC, but after going through it all it was found that getting started with an example Pega in a gadget is surprisingly quick and easy. Proceed as follows:

1. Obtain a Pega VMWare PVS system (I used the one from the Pega Academy SSA course, which is Pega 7.1.6). Obtain the Pega Composite Gateway .war file for that version of Pega - I phoned GCS in Reading to request it, and they emailed it to me. Start the VMWare system and log on to its console (username 'architect', password 'password'). Type 'ifconfig' on the command line, and record the ip address that the VMware instance is serving, in my case Proprietary information hidden. To make life easier, map this IP address to 'prpc' in your hosts file (add the line "  Proprietary information hidden   prpc " to the bottom of the text file C:\Windows\System32\drivers\etc\hosts ).
2. Determine PRPC task to embed in the mashup, and configure PRPC for this. Run the VMWare system, and log on to it with a browser (http://prpc:8080/prweb/PRServlet username='admin@sae', password='rules'). The Application on my system is called 'HRServices', and it has a case called 'Candidate' which is the process for a potential employee to register with name and address etc. I wish to embed this process in my mashup.

   1. The ruleset 'Pega-IAC:07-10-14' must be added to the Application 'HRServices' we are going to use. This ruleset is present ootb on PRPC 7, but it will not be in the Application stack by default, it must be added.

   2. Identify both the class and the starting flow of the Case we are to embed in the mashup. In  this case, it is 'SAE-HRServices-Work-Candidate.pyStartCase'.
   3. Create an operator for the mashup to use - just do a SaveAs of the 'admin@sae' operator you are using, I called mine 'operatorIAC@sae', and set its password to be 'rules7'.
   4. We need to add the line '<env name="Authentication/RedirectGuests" value="false"/>' into the Pega prpc 'prconfig.xml' file. I suggest you use a proper tty emulation rather than the VMWare console (PuTTY is good), the command 'find / -name 'prconfig.xml -print' will show you where it is, and use 'su' to select root account, password is 'password' and then use vi to add the entry. Reboot Pega, using the 'shutdown -h now' command and restarting VMWare afterward.
   5. All the rest of the configuration (the IAC Authentication Service, the IAC servlet etc.) is already present ootb, in Pega-7.
3. Install Tomcat on your laptop. There are lots of ways for doing this but the easiest is 'xampp' which can be downloaded for free and its installer will install it. Choose a directory, I installed mine in directory 'C:\xampp'. To make life easier, choose a directory name without space chars in it. Use the xampp console to start tomcat.
4. Install Pega Composite Gateway onto tomcat. This couldn't be easier, just copy your file 'prgateway.war' into the directory 'C:\xampp\tomcat\webapps', stop and restart tomcat. By default tomcat will be serving on 'localhost', so log on to the Pega Composite Gateway using http://localhost:8080/prgateway and you should see the Pega IAC Gateway Configuration Console. (Note, the prgateway console has a very Pega-6.2 look to it; this is normal, I have found only the Pega 7.19 version of prgateway looks like its Pega-7.)
5. Configure a Mashup Gadget. In prgateway, we  first configure a Host, then setup a Gadget, then Preview it.

   1. Click 'Host Configuration', enter a name for your connection e.g. 'PVSprpc', enter its host URL e.g. http://prpc:8080/prweb/PRServlet then enter its Auth Servlet http://prpc:8080/prweb/IAC , this Auth servlet is configured ootb in Pega 7. Hit 'Test Connection', you should get 3 green lights; hit 'Save Connection'.

   2. Click 'Gadget Setup', select the Host you have just configured, 'PVSprpc'. Enter the username and password of the prpc account to use 'operatoriac@sae', 'rules7' and Submit. Then wait a while! First-Use Assembly takes a surprising long time for the IAC rules. Eventually, the 'Gadget Generation' section appears.
   3. Configure your Gadget. Enter a name for it 'CandidateEntry', select Pega Action 'Create a new work object (createNewWork). Enter your class name 'SAE-HRServices-Work-Candidate', Display Model 'empty', Flow name 'pyStartCase'. In 'Advanced Settings', select Gadget Target '_self'. And that’s it. Note, open 'User Defined parameters', you should see the username you entered and the Password, encoded in base64. Use an online decoder, to decode the password and then verify that it IS the password for the user account you set up.
6. Preview the Mashup Gadget. Click the 'Preview' button. The preview window opens. In my case it contains "PRGateway Exception: error response from PRPC". To test your gadget without using prgateway, click 'Download Web Files' button, you are prompted to save a zip file containing your Gadget 'CandidateEntry.zip'. Save this file into a new directory elsewhere in your filesystem, 'C:\temp'.

   1. Open the 'CandidateEntry.zip' zipfile and extract the contents to disk, there are three files: 'CandidateEntry.html', 'PegaInternetApplicationComposer.js', and 'PegaInternetApplicationComposerLog.js'.

   2. Open 'CandidateEntry.html' using a text editor e.g. 'notepad++'. Un-comment the 5^th line <script src="PegaInternetApplicationComposerLog.js"></script> note this is html-style commenting. Comment out the prgateway URL on line 7, and comment in the direct prpc URL on line 8, we want the value pega.web.config.gatewayURL = "http://prpc:8080/prweb/PRServlet"; to be executed, note inside the <script> tag this is Java-style commenting.
   3. Save the file. Right-click on the file in the directory, and in the RH mouse menu select 'Open With … Firefox'.

   And your gadget opens, with the embedded new Candidate work object. A popup window also opens (check Firefox popups are enabled) containing the Gadget logging.