The Trumpet TCP/IP stack
Trumpet TCP/IP is a networking stack by Peter R. Tattam, published as a
"Free without support" package in 1992.
Two versions exist to my knowledge: version 2.01 and an improved version
called "ntcpdrv". They both share the same INT interface.
It is essentially a DOS TSR that exposes INT functions for performing a
variety of network operations (send a packet, establish a TCP connection,
receive a UDP datagram, etc). It requires a working packet driver.
BIN Trumpet TCP v2.01 (tcp201.zip)
BIN Trumpet NTCPDRV (ntcpdrv.zip)
TEXT Technical specifications (for developers)