How can I learn a multitouch screen's communication protocol and write a C# application for it?

Question

I have got a monitor with multitouch overlay on top of it. It works fine with Windows 7 but I want to write a multitouch application in C# for Windows XP which doesn't support touch feature out of the box. There is no documentation whatsoever and I emailed the manufacturer but never got a reply.

However the device works with Google Earth, which doesn't natively support multitouch, on Windows XP. So I think it generates many types of messages together i.e. WM_TOUCH for Windows 7, one for Google Earth COM API, and probably its own messages either in UDP or Windows message form. How can I trap all communications and learn the protocol?

Answer 1

OllyDbg is a very low-level debugger that allows you to see a lot of the messages going back and forth on the machine. I've seen it used to reverse-engineer a USB device driver's messages to figure out how to interact with an item.

I suspect that would be an excellent place to start. It should allow you to determine how the messages are being passed and, perhaps, start teasing apart their structure.

Answer 2

There are solutions like Tuio around that do not rely on Windows 7. Maybe a tuio (or alternative) implementation would make you life easier.