In the January 2001 issue, I discussed how to integrate e-RPG with Microsoft Windows IIS Web server pages (see “Integrating E-RPG with Windows IIS,” MC, January 2001). E-RPG is the name given to the technique that incorporates OS/400 HTTP APIs into RPG programming so that the program accepts standard browser-client input and returns formatted HTML output (including OS/400 data) to a browser. The e-RPG program acts as a CGI program to deliver OS/400 data to a browser.
Since a large number of shops use Windows IIS for Web serving (approximately 25 percent of the active Web sites in the world, according to Netcraft’s latest Web Server survey, www.netcraft.com/survey), there is a high interest among OS/400 shops in implementing this solution and, I received a lot of requests for clarification and expansion on e-RPG-Windows IIS integration. So this month, I’ll look at some questions I received about this new technique from Midrange Computing Forum users (www.midrangecomputing.com/forums) and see what answers I can come up with.
Q: I don’t understand how you merge Windows processing with OS/400 processing. Your technique sounds more like Web-page redirection to me.
A: The solution’s intention is to create an HTTP Server for OS/400 instance that only serves RPG CGI programs (e-RPG). It allows you to use your Windows IIS server for HTML processing—along with any other Web application server processing you have installed on that Windows IIS server (such as the Macromedia oldFusion Web application server)—while also retaining Web access to OS/400 data through e-RPG programs. You could call up a Windows IIS HTML form that contains data from an SQL Server, and then, by pressing the Submit button, send that SQL Server data to your iSeries (AS/400) for further processing and present the user with a returned HTML page that features merged IIS and OS/400 data. You’re right. It is a redirection that enables cooperative processing between the two environments.
Q: You refer to “...calling programs from a Windows IIS Server” and “...delivering output and RPG programs to a Windows IIS Server.” Windows IIS never calls an e-RPG program under your proposal. Instead, the browser alternatively makes a request of either IIS or e-RPG. You’ve just proposed a solution where some content is served by IIS and other content is served by the HTTP Server for AS/400.
A: Unfortunately, I misspoke in the first article; the solution exists exactly as you explained here. When I referred to Windows IIS servers in the earlier article, I should have said “Windows IIS server users” because this technique is reliant on the e-RPG programs being kicked off from IIS-delivered browser pages. It helps to clearly explain and understand how the IIS-to-e-RPG scenario works:
1. The client browser downloads an HTML form from the Windows IIS server. The form is displayed on the browser. This form can also include hidden fields that contain data retrieved from a Microsoft-based data source (such as Microsoft SQL Server).
2. The user fills out the form and clicks the Submit button.
The browser uses the POST method to send the form data to an e-RPG program on your AS/400. The important point is that the browser sends the request to the AS/400, not to the Windows IIS server, which means the browser must be able to reach your iSeries (AS/400).
3. The HTTP Server for AS/400 CGI-only server instance accepts the input and compares the incoming URL against its Request Routing directives. If a match exists, the server instance transforms the incoming URL to an OS/400 program call to the e-RPG program.
4. The e-RPG program runs, processes the incoming data (which includes the Microsoft database information that was also passed as hidden form fields), combines it with OS/400 data, and creates an HTML output file that is then sent back to the requesting client browser.
5. The browser receives the HTML file and displays it. Depending on how you programmed your e-RPG HTML output, you could include Next and Back buttons for more OS/400 data or links to the Windows IIS Server for more processing.
Alternatively, you could reverse the flow and use e-RPG to download OS/400 data in an HTML page to a user, who can then click and pass that data to a Windows IIS Active Server Page document that combines the OS/400 information with Microsoft-based data.
And So It Goes...
This Microsoft IIS-to-e-RPG technique is difficult to explain, but it can be a valuable tool for Microsoft-OS/400 integration. If you’re interested in using e-RPG techniques in a Windows environment, I encourage you to experiment with this technique and let me know what your results are. In addition to other OS/400-to-Windows techniques—such as ODBC and OLE DB access—it has a place in your OS/400 networking toolbox.
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