ucspi-unix binary package in Ubuntu Focal amd64

 unixclient and unixserver are command-line tools for building UNIX
 domain client-server applications. unixclient connects to a UNIX domain
 socket and runs a program of your choice. unixserver creates a UNIX
 domain socket, waits for incoming connections and, for each connection,
 runs a program of your choice.
 .
 unixclient and unixserver conform to UCSPI, the UNIX Client-Server
 Program Interface, using UNIX domain sockets. UCSPI tools are available
 for several different networks.
 .
 See http://cr.yp.to/proto/ucspi.txt for more information on UCSPI.

Source package