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 ddfa(7)                                                             ddfa(7)

 NAME    [Toc]    [Back]
      ddfa - Data Communications and Terminal Controller (DTC) Device File
      Access (DDFA) software

 DESCRIPTION    [Toc]    [Back]
      The Data Communications and Terminal Controller (DTC) Device File
      Access (DDFA) software allows access from HP-UX system utilities and
      user applications to terminal servers using standard HP-UX structures.
      DDFA provides an interface to remote LAN-connected terminal server
      ports that is similar to the interface for local directly-connected

      The basic principle is that a daemon is created for each configured
      terminal server port based on information in a configuration file (a
      Dedicated Ports file).  When the daemon is spawned, it takes a pty
      from the pool and creates a device file with the same major and minor
      number as the pty slave.  The device file is known as the "pseudonym"
      and utilities and applications use the pseudonym to access the
      terminal server port by exercising standard HP-UX system functions
      (open(), close(), read(), write(), and ioctl()).  The daemon listens
      on the pty until an application does an open() on the pseudonym.  It
      then sets up and manages the connection to the terminal server port
      until the application does a close() on the pseudonym.  The end result
      is that the terminal server port is addressed via a device file, but
      the mechanism that makes it happen is transparent to the user.  A
      second configuration file (a port configuration file) contains
      information to profile the terminal server port.

      DDFA consists of the following items:

           dp             Dedicated Ports file.  This text file contains the
                          information that DDFA needs to set up and manage a
                          connection between a pseudonym and a terminal
                          server port.

                          The dp file is parsed by the Dedicated Port Parser
                          (dpp) which spawns an Outbound Connection Daemon
                          (ocd) for each outbound connection specified in
                          the file.  The dp file is also used by the HP-UX
                          Telnet daemon (telnetd) to identify incoming
                          connections from a DTC and map them to a pseudonym
                          (the Telnet port identification feature).

           pcf            Port Configuration File.  This text file is used
                          by DDFA to profile the terminal server port.  The
                          generic name of the template file is pcf.  A port
                          configuration file is referenced by an entry in
                          the Dedicated Ports file (dp).

           dpp            Dedicated Port Parser.  This command parses the
                          Dedicated Ports file (dp) and spawns an Outbound

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 ddfa(7)                                                             ddfa(7)

                          Connection Daemon (ocd) for each valid entry in
                          the dp file.  It can be run from the shell or it
                          can be included in a system initialization script
                          to automatically run the DDFA software each time
                          the system is booted.

           ocd            Outbound Connection Daemon.  This daemon manages
                          the connection and data transfer to the remote
                          terminal server port.  Normally, it is spawned by
                          the Dedicated Ports Parser (dpp), but it can be
                          run directly from the shell.

                          As it starts, it creates its pseudonym for the
                          connection.  As it terminates normally, it removes
                          the pseudonym.  If the pseudonym is removed while
                          it is running, ocd will terminate with an error

           ocdebug        Outbound Connection Daemon debug mode.  This is a
                          special version of ocd that contains debugging
                          code.  It must be run from the shell.

 CONFIGURATION    [Toc]    [Back]
      There are two basic steps to configuring the DDFA software:

        +  Enter information in the dp file.

        +  Enter information in the port configuration files.

    Configuring the dp File    [Toc]    [Back]
      The dp file contains one line for each outbound connection that is to
      be established and one line for each incoming connection request.  A
      default file /usr/examples/ddfa/dp should be copied to a new file and
      the copy edited as needed.  It is recommended that a directory be
      created to hold the dp file and the port configuration files.

      Each line of the dp file must contain the location of the terminal
      server port and the location of the pseudonym.  In addition, for an
      outbound connection, the port configuration file must be specified and
      a logging level may be specified.

    Configuring the Port Configuration Files    [Toc]    [Back]
      A port configuration file is used to configure individual terminal
      server ports.  A master port configuration file is
      /usr/examples/ddfa/pcf.  In practice, it is renamed for each port that
      needs different configuration values and the values are altered
      appropriately for the device attached to the port.  It is recommended
      that a directory be created to hold the port configuration files and
      the dp file.

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 ddfa(7)                                                             ddfa(7)

      Each line of a port configuration file must consist of a name of a
      variable and its value.  The variable-value pairs contain information
      on how to open a connection to a terminal server port, how to close a
      connection to a terminal server port, and how to manage the data
      transfer to a terminal server port.

    Configuring a System Initialization Script    [Toc]    [Back]
      DDFA can be run at boot time by including a reference to dpp in a
      system initialization script.  It is recommended that the -k option be
      used when running dpp in this environment.

 KILLING DAEMONS    [Toc]    [Back]
      Note that ocd should be killed using kill -15.  Do not use kill -9 for
      this purpose as it does not remove the device file.  ocd verifies the
      validity of an existing pseudonym before trying to use it.  dpp and
      ocd use data stored in the file /var/adm/utmp.dfa to verify whether a
      process still owns a pseudonym before taking it over.  If ocd finds an
      unowned pseudonym, it uses it.

 ERROR HANDLING    [Toc]    [Back]
      When ocd receives a serious error condition, such as when the LAN goes
      down, it transmits the error condition to the application by closing
      the pty.  Any open(), close(), read(), or write() to the pseudonym
      returns the error condition 0 bytes read.  If the pseudonym is the
      controlling terminal for the group to which the application belongs,
      SIGHUP is sent to all the processes in the group, including the

      Not all ioctl() functionality is available, due to the lack of a
      protocol that allows the transmission of such commands over the LAN to
      the remote port.

    termio Attribute Limitations
      The main restrictions on termio attributes (see termio(7)) include
      modem signal control and parity checking.  The following are not


    ioctl() Request Limitations
      The following ioctl() request limitations apply:

           CSTOPB flag         DTC only supports one stop bit.

           CSIZE               DTC only supports 8 bits per character.
                               Value cannot be modified.

           PARODD flag         DTC offers static configuration to handle
                               even or odd parity.  It also handles auto
                               parity detection for even or odd parity.

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 ddfa(7)                                                             ddfa(7)

           PARENB flags        Enabling/disabling done via static
                               configuration.  No programmatic interface

           INPCK flag          No way to separate input from output parity

           IGNPAR flag         Cannot be configured on DTC.

           PARMRK              Bad characters are forwarded to the system
                               without marking them with OFFH or OH.

           CBAUD               Speed is part of static configuration.

           IXOFF flag          Flow control is enabled if the DTC static
                               configuration specifies an ASCII access mode.
                               If binary is selected, no flow control is

           IXON flags          Pacing of output to a terminal via a
                               programmatic interface is enabled when ASCII
                               mode is selected in static port configuration
                               and disabled when binary mode is selected.

           IXANY flag          DTC does not offer the ability to restart
                               output on any character received if XOFF was
                               previously received.

           HUPCL flag          DDFA does not support the hanging up of modem
                               signals on the last close of the device file.
                               If the modem signals used on the DTC drop,
                               the connection is closed.

           CLOCAL flag         Not supported.

           c_flags             IENQACK not supported.

                               OFILL, OFDEL, NLDLY, CRDLY, TABDLY, BSDLY,
                               FFDLY not supported by Telnet port
                               identification software.

           BINARY mode flags   Part of static configuration is done in DTC
                               Manager by selecting binary mode.  If
                               switching is enabled, binary can be selected
                               at user interface level.  There is no way to
                               automatically negotiate binary mode when
                               proper termio flags are reset when using
                               telnetd.  Binary/ASCII switching is possible
                               with DDFA.  The DTC cannot support large
                               reads in pure binary mode, so transferred
                               blocks of data should not be more than 256

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 ddfa(7)                                                             ddfa(7)

                               bytes.  If half-duplex with remote
                               acknowledgement is implemented, binary
                               applications can be supported.

    ioctl() System Call Requests
      The following ioctl() system call limitations apply:

           TCSBRK              The ability to send a break without waiting
                               for previous data to be sent is not provided
                               at the system level in telnetd or DDFA.
                               Receiving a Telnet break command in the DTC
                               allows it to generate a break on asynchronous

           TCFLSH              The DTC output queue cannot be flushed.

           Hardware handshake request
                               Not supported on DTC.

           TCXONC              Local handshake cannot be disabled on DTC.

           MCGETA              Not supported.

                               There is no way to separately set modem lines
                               of a DTC port.

           MCGETT              Modem timers, CD timer, connect timer, and
                               disconnect cannot be configured.

           CCITT simple, and direct call-in/call-out modes
                               DTC cannot handle simple mode because there
                               is programmatic interface for modem signals.
                               Call-in mode cannot be simulated if the port
                               is opened, because modem signals (or the
                               call) must be present within 2 minutes or the
                               connection is cleared.

           DACIDY get device adapter info
                               No way to get device adapter information.

           Download ioctl() DACRADDR, DACDLADDR, DACDLGO, DACDLVER
                               No programmatic call to download the DTC.

                               No programmatic interface to get such info.

           DACLOOPBACK DACSUBTEST port test

 WARNINGS    [Toc]    [Back]
      In order to ensure that commands (such as ps) display the correct

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 ddfa(7)                                                             ddfa(7)

      device file name (that is, the pseudonym), all pseudonyms should be
      placed into the directory /dev/telnet.  If pseudonyms are not
      specified for placement in this directory, the correct display of
      device file names with many commands is not guaranteed.

      In addition, in order to ensure that commands (such as w, passwd,
      finger, and wall) work correctly, each pseudonym must be unique in its
      first 17 characters (including the directory prefix /dev/telnet/).  If
      pseudonyms are not unique in their first 17 characters, the correct
      functioning of many commands is not guaranteed.

      Also, in order to reliably handle timing mark negotiations (and ensure
      that files printing on a printer attached to a terminal server have
      been completely flushed to that printer), the following line must be
      added near the end of each printer interface script for printers
      attached to a terminal server:

           stty exta <&1 2>/dev/null

      The printer interface scripts reside in the directory
      /etc/lp/interface.  The line must be added just prior to the final
      exit command in each printer interface script.

      If this line is not added as specified, the printing reliability of
      printers attached to a terminal server is not guaranteed.

 FILES    [Toc]    [Back]

 SEE ALSO    [Toc]    [Back]
      dpp(1M), ocd(1M), ocdebug(1M), ioctl(2), dp(4), pcf(4), ioctl(5),

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[ Back ]
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