Now you can use the CPortX activeX control in SWFKit or SWFKit Pro to access serial ports.
Download
The query modem sample
Note:
You must use the CPortX in SWFKit Pro (SWFKit) ver 2.2 or later. For SWFKit 2.2 isn't released yet, please get a special edition of SWFKit Pro that can use the CPortX ActiveX object at
http://www.swfkit.com/download/swfkit.exe