I have to re-implement an existing system from scratch.
At one point, when the user navigates to a certain web page the server must read data from the user's serial port.
Currently, the web page has an ActiveX control; when the page is loaded the ActiveX control calls into a COM DLL on the user's PC which reads data from the serial port.
The system is 10 years old. Is there any "better" way that I could implement this?
For instance, technology has move on in the last ten years. And this solution seems only to work in MS IE, which now has a market share of about 26% (it had, in 2013, when I last updated this question. As of Feb 2107, MS IE has 3-4% and Edge has 1-2%. As Edge is also a MS product, it might support Active X - I have not tried. Otoh, since it is new from the ground up, there is a good chance that it does not).
Did HTML 5 offer any new possibilities? What about products like Cordova?
Are there any other possibilities?
Could I add a Raspberry Pi to do the reading over serial port & and have the browser app communicate with that over a RESTful service?
[Update] @ EuroMicelli said "I'm going to assume that you have a very good reason to run your app from a web browser, instead of a native app". I don't know as I wasn't around when the original project was planned (and the company which designed it is now defunct).
Perhaps they didn't want the end user interfacing directly with the database? Perhaps "browser based" was a new buzzword back then? I, personally, have no problem with a desktop app (as I find them easier to implement), but maybe we should consider remaining browser based? (besides, I can handle the desktop app myself; it's only browser based reading from the COM port that leads me to offer a bonus ;-)
Just to name another (more like "web-of-things") option: external hardware.
Depending on the use-case you COULD use an external low cost device like an arduino microcontroller or raspberry-pi embedded pc.
It's not very difficult to build a simple serial to web-service bridge upon these kind of devices. You could use some projects like this e.g. : https://code.google.com/p/serwebproxy/
In such a scenario all the low level stuff is handled by the external hardware and is offered to you by a web-service like interface (via get/post).
Further advantage is that the pc, where you application runs on, doesn't need a serial port (which becomes quite rare on some systems).
From your browser application you could query the web-service on the embedded device with a simple ajax call. The browser wouldn't need any plugin at all, the solution works cross plattform and is generic and independent from the development of browser-technologies in the near future.