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A computer that has many serial ports (with many serial cables
connected to it) is often called a server. Of course, most servers
serve other functions besides just serving serial ports, and many do
not serve serial ports at all (although they likely have a serial port
on them). For example, a "serial server" may have serial cables,
each of which runs to a different (non-serial) server. The serial
server (perhaps called a "console server") controls, via a console,
all the other servers. The console may be physically located remote
from the serial server, communicating with the server over a network.
There are two basic types of serial servers. One type is just an
ordinary computer (perhaps rack mounted) that uses multiport cards on
a PCI bus (or the like). The other type is a proprietary server that
is a dedicated computer that serves a special purpose. Servers of
both types may be called: serial servers, console servers, print
servers, or terminal servers. They are not the same.
The terminal server was originally designed to provide many serial
ports, each connected to a dumb text-terminal. Today, a terminal
server often connects to graphic terminals over a fast network and
doesn't use serial ports since they are too slow. One network cable
takes the place of many serial cables and each graphic terminal uses
far more bandwidth than the text-terminals did. However, graphic
terminals may be run in text mode to reduce the bandwidth required. A
more detailed discussion of terminal servers (serial port) is in
Text-Terminal-HOWTO. For networked terminal servers (not serial port)
see
Linux Terminal Server Project (LTSP)
(To-do: Discuss other types of serial servers, but the author knows
little about them.)
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