As you already have found out, you need an ODBC driver.
Merant is the company that took over Intersolv.

Also, though, you need the Informix middleware, that they lovingly call Informix-Net (or I-Net). Of course, it's from Informix.

And, yes, it all seems to work. I haven't tried it now in 2 or 3 years, but it used to work fine for me.