sslserver, sslclient, and sslhandle are command-line tools for building
SSL client-server applications. They conform to the UNIX Client-Server
Program Interface, UCSPI.

sslserver listens for IPv6 and/or IPv4 connections, and runs a program
for each connection it accepts. The program environment includes
variables that hold the local and remote host names, IP addresses,
and port numbers. sslserver offers a concurrency limit on acceptance
of new connections, and selective handling of connections based on
client identity supporting CIDR IP address notation. sslserver supports
STARTTLS and STLS.

sslclient requests a connection to either a IPv6 or IPv4 TCP sockets,
and runs a program. The program environment includes the same variables
as for sslserver.