RJT>> I wonder if there's something similar for dos?

 ml>> the closest is RL-FOSSIL...

 RJT> And what does that one do?  Look like a modem to the
 RJT> application while talking to a NIC?

yes, that's what all virtual modem shims do... but not necessarially to a
NIC... more like to the tcp/ip protocol stack... the problem with DOS ones
is that there are several tcp/ip protocol stacks and they are not
compatible with each other... not compatible in that programs coded for one
will not work with another... i'm aware of two, possibly three, stacks for
DOS... actually, that may be three, possibly four... i have run the m$
workgroup addon stack with netbios and tcp/ip on a DOS only machine and
even had a DOS 5 workgroup server... no windows software at all...

)\/(ark