"Soft" ethernet modem?

I am using Digi PortServer TS MEI in modem emulation mode, to encapsulate PPP session over Ethernet.

In my system, at one end of the line I have a PPP-capable device + the PortServer TS, and on the other end I have a Windows box + another PortServer TS. The Windows box is configured to accept dial-in requests, and to dial-out on demand. Now, it is a waste of hardware to have that second PortServer TS attached to the Windows box. Is there by chance a sort of “software modem”, i.e. an application that encapsulates the telnet session, implements all AT commands as expected, and shows up in Windows as another COM port with attached modem?

Did you tried any virtual modems Software>

Yes, the com port redirection software is known as Realport. Here is a link to the driver page for Windows x86/x64:

http://www.digi.com/support/productdetl.jsp?pid=1950&osvid=57&tp=1&s=233

(driver is for Windows XP, Server 2003, and Vista x86/x64)