Call COM port from webpage

I'm looking for a way to call a COM port from a webpage.

I was thinking abut running a Java WebStart (or Flash?) program that opens a local web server that allows to interact with the COM port using JSONP.

Are there any show stopping security restrictions on the way that I don't know of? This should be possible:

use native libraries (Java COM bridge) from Java WS application
open a local port
access local port from javascript, likely using <script> tags
do all this without scaring users with "This website is trying to do something really nasty, get off as fast as you can" kind of messages :)

I've used a Java COM bridge before, so this shouldn't be the problem - at least as soon as I'm able to run native code.

So how would my JNLP file have to look like to get this working? Any alternatives to Java WS? Better install it as a daemon?

Solution

This article answers the first part of my question, the WS to COM approach that is: Juggling with DLLs, WebStart and Maven

Accessing an HTTP server on a local port should also be feasible as that's what Playdar does for instance.