Anyone know of an end-to-end modem emulator which supports AT commands?

I've tried several Windows products but none seem to work with Cygwin. Something native to Linux and Unix is preferable.

And since this is for testing code that needs to interact with many local modems the emulated devices need to be available as local TTY devices.

Qtopia's Phonesim and Atinterface are unavailable as they took the code down.

Dosbox looked promising but the local interface is only available within the emulated DOS environment.