A fairly complete implementation of a various network protocols for ZX Spectrum, written from scratch in Z80 assembly. Includes serial-line emulation on parallel port (38.400 bps), chat-script interpreter, PPP protocol (LCP, NCP), IP and ICMP, UDP and TCP protocols. Comparing to many todays implementations, e.g. uIP, it is a REAL implementation of those protocols (i.e. it does defragmentation etc.) unlike the understand-some-headers software currently available [(c) 1998 Milan Pikula, Juraj Rehak, Lubos Janica]

http://www.ipsec.info/~www/software/ppp_tcpip.tar.gz