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Office Server AX4000
Examples of Use
Last Update: 12/03/2004
The Axel Office Server is a communication server specifically designed for Ethernet TCP/IP networks. Standard services are offered by this product to support devices such as serial dumb terminals and printers, but the Axel Office Server can also be used in many other ways, as shown below. These are examples of use:
  - connecting dumb terminals
  - connecting printers
  - connecting other devices
  - managing a modem pool
  - connecting two serial devices through the network
  - connecting TCP/IP text-terminals to a non-TCP/IP host


Connecting Dumb Terminals 

Serial dumb terminals can be connecting to a TCP/IP host through the Axel Office Server. These dumb terminals can be either directly attached to the Office Server or located in a remote site (connection via modem, leased line, etc).

 

How does it work ?

The Office Server’s port(s) to be connected to the serial terminal(s) is set with the telnet client service. This service allows immediate support for the serial terminal (no specific operation is needed at the operating system level).

Furthermore, the Office Server is able to manage locally a remote site (modem, leased line, etc). The line parameters are entered through the Office Server's set-up. So, the operating system on which the serial terminal is connected "sees" the line as a direct line.

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Connecting a Printer

Printers connected to the Office Server are accessed by all network hosts as a standard system printer (printers are shareable and managed by the spooler).

 

How does it work ?

The Office Server’s port(s) to be connected to the printer(s) is set with the 'lpd' service. The main benefit is the LPD protocol is provided as a standard feature by the major operating systems (Unix, AS/400, Windows NT...). No additional software is needed.

Furthermore, a LPD printer can be shared by many hosts (the LPD Office Server serial port is "locked" only during the printing).

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Connecting Other Devices

The Office Server’s serial ports can be seen as local ports by the operating system. This means that any software can control the Office Server’s ports (like the ports on a local multi I/O board). This allows any serial device to be connected on the network using existing cabling.

 

How does it work ?

The Office Server’s serial ports are seen as local ports via a driver installed on the operating system (available for Unix and Windows). On Unix, the Office Server's ports are seen as "ttys". On Windows they are seen as additional "COM" ports.

With some Unix systems (AIX, Linux...), the port is controlled only by the dataflow (bi-directional flow). This allows support for most of devices (card readers, scales, automates...).

For SCO Openserver and Windows (95, 98 and NT 4), ports are fully controlled, so any software can use standard operating system commands:
   - to set serial line parameters (baud rate, parity, etc),
   - to set serial output signals (DTR and RTS),
   - to get serial input signal status (DSR, CTS and CD).

This gives full control over the modem/modem pool (see next section).

Technical Notes
- a standard protocol: the port full-control is given by the RFC 2217 protocol which is a telnet protocol extension (telnet server protocol and RFC 2217 extension are Office Server embedded protocols).
Note: RFCs can be consulted at ftp://ftp.merit.edu/documents/rfc.
- serial port identification: each of the Office Server’s ports using the "telnet server" is given a unique numeric identifier called the "TCP port". So with both the "Office Server IP address" and the "TCP port" each port on the Office Server can be uniquely identified across the network.
- a shareable port: the Office Server channel is "locked" by a host only during use. When the tty (or the COM) is closed by the operating system, the Office Server channel becomes available for any network hosts. This allows a channel to be shared between hosts (for instance, concurrent access to a modem).

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Modem Pool

As shown below, any network host can access a modem pool attached to the Office Server. This pool is locally managed by the Office Server. When a computer needs a modem, the Office Server "gives" the first available modem.

 

How does it work ?

The Office Server’s ports are seen as local ports on each network host (see "technical notes" protocol in the Connecting other Devices section).

To use a local modem pool, multiple Office Server ports need to be associated with the "telnet server" and set with the same "TCP port". So, networked computers see a single virtual port and the Office Server redirects requests to the first available modem.

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Connecting Two Serial Devices through the Network

As shown below, the two serial devices are connected to the network and are able to exchange data. This allows the use of existing network cabling, or to have one serial device a great distance away from the other, by "embedding" a TCP link in the serial line.

 

How does it work ?

Two Office Servers are needed. One is used as a client, the other is used as a server (services: telnet client and telnet server). With these settings, the channel of the "client" Office Server automatically opens a connection to the channel of the "server" Office Server. So the two devices are able to communicate as a direct connection.

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Connecting TCP/IP Text Terminals to a non-TCP/IP Host

As shown below, the TCP/IP text terminal can open connections to both a TCP/IP host and to a non-TCP/IP host (no Ethernet board available). This can be useful, when a site is migrating from a non-TCP/IP installation to TCP/IP (the text terminal can access to the two hosts during the migration period).

 

How does it work ?

To access the non-TCP/IP host, the text terminal opens a connection with the Office Server where a channel is set as "telnet server". The Office Server acts as an interface between the serial connection and the network. At the non-TCP/IP host level, the TCP/IP terminal is seen as a serial terminal.

This technique allows several TCP/IP terminals to be seen by the non-TCP/IP host as serial terminals. Each TCP/IP terminal opens a connection to "its" serial port (like with a serial multi I/O board). This is allowed by associating a different TCP port with each Office Server channel set as telnet server.

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Email: info@axel.com