Re: Crazy little web project -- RPG400-L

Bob Cozzi wrote:

There's an old saying "If it ain't broke, don't fix it" I've always felt that was said by a jacka$$. The saying that I like is: "If it ain't broke, you ain't looked hard enough!" What's wrong with the wheel? Well, there's too much excess rubber, recycling isn't at 100% yet, it goes flat, even in 2004, and on and on. Why reinvent it? To solve these and many other problems that are overlooked simply because we're used to them. Building a webserver will give whoever does it, the pleasure of learning more about the way things work in programs such as Apache (for example) than most of us will learn in our lifetimes out it. Thus that person may choose to share that knowledge with others; and there's always the possibility that they could improve existing technology through the discovery process. I think it's a great idea. -Bob Cozzi

Well I'm sure the great Canadian philosopher Red Green once said "If it ain't broke, you're not trying hard enough". But I'm sure he wasn't the first to make that observation.

I don't want to discourage anyone from trying to develop a new HTTP server, but as others have pointed out, it's already been done. And the whole WWW benefits from the existing servers, especially the open-source Apache.

Fact is, there are lots of ways to implement HTTP servers. Using Python, it's possible to implement an HTTP server in as few as 3 lines of code. (I know - I've done it myself! You basically just instantiate a CGIHTTPServer object.)

But an HTTP server in RPG? Well, one bottleneck you'll likely run into is the fact that RPG has limitations running in a threaded environment. RPG programs are generally non-reentrant. The best you can do is code the THREAD(*SERIALIZE) option which ensures that a module is active in only one thread at one time. Threading is normally needed in a server program to give speedy response to each request.

I've argued this point before, but if you want to do systems programming, you're way better off using a language that's better suited to systems programming, like C. RPG is best suited to applications programming, which has entirely different needs. The fact that you *can* do calls to system API's in RPG doesn't mean you *should* call them from RPG!

By all means, don't shy away from implementing your own HTTP server. But IMHO, you'll learn more about the HTTP by coding it in C. If you want to learn more about RPG programming, then choose a problem in the application programming domain.

Cheers! Hans

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