This program provides a convenient way to manage many remote serial
consoles for machines.  A server (conserver(8)) runs on each server
machine and it connects to the specified serial port.  It can log,
provide shared access to remote consoles, etc.  If there are multiple
machines running conserver(8), a master conserver(8) can be run to
connect to all the slave servers, providing a single point of access
to the entire cluster.

This is very handy for remote unattended FreeBSD servers.  It can send
serial break signals which is useful for breaking into DDB on hung machines.