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6. Servers for Serial Ports

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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