sslserver and sslclient are command-line tools for building SSL client-server applications. They conform to the UNIX Client-Server Program Interface, UCSPI. sslserver listens for 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. sslclient requests a connection to a TCP socket, and runs a program. The program environment includes the same variables as for sslserver.