NetFoss is a popular Network FOSSIL driver for Windows.
A FOSSIL

FOSSIL

FOSSIL is a standard protocol for allowing serial communication for telecommunications programs under the DOS operating system. FOSSIL is an acronym for Fido Opus SEAdog Standard Interface Layer. Fido refers to FidoBBS, Opus refers to Opus-CBCS BBS, and SEAdog refers to a Fidonet compatible mailer...

 is a serial communications layer to allow DOS based software to talk to modems without dealing with hardware I/O and interrupts.

A Network FOSSIL redirects such software to a TCP/IP address rather than to a serial modem.
NetFoss is faster than other FOSSIL drivers, due to being written in 32-bit assembly language

Assembly language

An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...

.
It allows Zmodem

ZMODEM

ZMODEM is a file transfer protocol developed by Chuck Forsberg in 1986, in a project funded by Telenet in order to improve file transfers on their X.25 network...

 transfers at up to 280,000 CPS.

NetFoss was developed in 2001 by pcmicro

Pcmicro

pcmicro was a large Bulletin Board System support site from 1981 to 1998. Before the World Wide Web became popular, the pcmicro BBS served as a central file repository for all non-commercial BBS software and related utilities...

, and was released as freeware

Freeware

Freeware is computer software that is available for use at no cost or for an optional fee, but usually with one or more restricted usage rights. Freeware is in contrast to commercial software, which is typically sold for profit, but might be distributed for a business or commercial purpose in the...

. Several minor updates have been released since then. The current version can be downloaded from http://netfoss.com.