nameserv(n)                  Name service facility                 nameserv(n)



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NAME
       nameserv - Name service facility, Client

SYNOPSIS
       package require Tcl  8.4

       package require nameserv  ?0.4.2?

       package require comm

       package require logger

       ::nameserv::bind name data

       ::nameserv::release

       ::nameserv::search ?-async|-continuous? ?pattern?

       ::nameserv::protocol

       ::nameserv::server_protocol

       ::nameserv::server_features

       ::nameserv::cget -option

       ::nameserv::configure

       ::nameserv::configure -option

       ::nameserv::configure -option value...

       $result destroy

       $result filled

       $result get name

       $result names

       $result size

       $result getall ?pattern?

_________________________________________________________________

DESCRIPTION
       Please read Name service facility, introduction first.

       This package provides a client for the name service facility
       implemented by the package nameserv::server.

       This service is built in top of and for the package comm.  It has
       nothing to do with the Internet's Domain Name System. If the reader is
       looking for a package dealing with that please see Tcllib's packages
       dns and resolv.

API
       The package exports eight commands, as specified below:

       ::nameserv::bind name data
              The caller of this command registers the given name as its name
              in the configured name service, and additionally associates a
              piece of data with it. The service does nothing with this
              information beyond storing it and delivering it as part of
              search results. The meaning is entirely up to the applications
              using the name service.

              A generally useful choice would for example be an identifier for
              a communication endpoint managed by the package comm. Anybody
              retrieving the name becomes immediately able to talk to this
              endpoint, i.e. the registering application.

              Of further importance is that a caller can register itself under
              more than one name, and each name can have its own piece of
              data.

              Note that the name service, and thwerefore this command, will
              throw an error if the chosen name is already registered.

       ::nameserv::release
              Invoking this command releases all names (and their data)
              registered by all previous calls to ::nameserv::bind of this
              client. Note that the name service will run this command
              implicitly when it loses the connection to this client.

       ::nameserv::search ?-async|-continuous? ?pattern?
              This command searches the name service for all registered names
              matching the specified glob-pattern. If not specified the
              pattern defaults to *, matching everything. The result of the
              command is a dictionary mapping the matching names to the data
              associated with them at bind-time.

              If either option -async or -continuous were specified the result
              of this command changes and becomes the Tcl command of an object
              holding the actual result.  These two options are supported if
              and only if the service the client is connected to supports the
              protocol feature Search/Continuous.

              For -async the result object is asynchronously filled with the
              entries matching the pattern at the time of the search and then
              not modified any more.  The option -continuous extends this
              behaviour by additionally continuously monitoring the service
              for the addition and removal of entries which match the pattern,
              and updating the object's contents appropriately.

              Note that the caller is responsible for configuring the object
              with a callback for proper notification when the current result
              (or further changes) arrive.

              For more information about this object see section ASYNCHRONOUS
              AND CONTINUOUS SEARCHES.

       ::nameserv::protocol
              This command returns the highest version of the name service
              protocol supported by the package.

       ::nameserv::server_protocol
              This command returns the highest version of the name service
              protocol supported by the name service the client is currently
              connected to.

       ::nameserv::server_features
              This command returns a list containing the names of the features
              of the name service protocol which are supported by the name
              service the client is currently connected to.

       ::nameserv::cget -option
              This command returns the currently configured value for the
              specified -option. The list of supported options and their
              meaning can be found in section OPTIONS.

       ::nameserv::configure
              In this form the command returns a dictionary of all supported
              options, and their current values. The list of supported options
              and their meaning can be found in section OPTIONS.

       ::nameserv::configure -option
              In this form the command is an alias for "::nameserv::cget
              -option]".  The list of supported options and their meaning can
              be found in section OPTIONS.

       ::nameserv::configure -option value...
              In this form the command is used to configure one or more of the
              supported options. At least one option has to be specified, and
              each option is followed by its new value.  The list of supported
              options and their meaning can be found in section OPTIONS.

              This form can be used only as long as the client has not
              contacted the name service yet. After contact has been made
              reconfiguration is not possible anymore. This means that this
              form of the command is for the initalization of the client
              before it use.  The command forcing a contact with the name
              service are

              bind

              release

              search

              server_protocol

              server_features

CONNECTION HANDLING
       The client automatically connects to the service when one of the
       commands below is run for the first time, or whenever one of the
       commands is run after the connection was lost, when it was lost.

       bind

       release

       search

       server_protocol

       server_features

       Since version 0.2 of the client it will generate an event when the
       connection is lost, allowing higher layers to perform additional
       actions. This is done via the support package uevent. This and all
       other name service related packages hereby reserve the uevent-tag
       nameserv. All their events will be posted to that tag.

EVENTS
       This package generates only one event, lost-connection. The detail
       information provided to that event is a Tcl dictionary. The only key
       contained in the dictionnary is reason, and its value will be a string
       describing why the connection was lost.  This string is supplied by the
       underlying communication package, i.e. comm.

OPTIONS
       The options supported by the client are for the specification of which
       name service to contact, i.e. of the location of the name service.
       They are:

       -host name|ipaddress
              This option specifies the host name service to contact is
              running on, either by name, or by ipaddress. The initial default
              is localhost, i.e. it is expected to contact a name service
              running on the same host as the application using this package.

       -port number
              This option specifies the port the name service to contact is
              listening on. It has to be a positive integer number (> 0) not
              greater than 65536 (unsigned short). The initial default is the
              number returned by the command ::nameserv::common::port, as
              provided by the package ::nameserv::common.

ASYNCHRONOUS AND CONTINUOUS SEARCHES
       Asynchronous and continuous searches are invoked by using either option
       -async or -continuous as argument to the command ::nameserv::search.

       Note that these two options are supported if and only if the service
       the client is connected to supports the protocol feature
       Search/Continuous. The service provided by the package
       ::nameserv::server does this since version 0.3.

       For such searches the result of the search command is the Tcl command
       of an object holding the actual result. The API provided by these
       objects is:

       Options:

              -command command_prefix
                     This option has to be set if a user of the result object
                     wishes to get asynchronous notifications when the search
                     result or changes to it arrive.

                     Note that while it is possible to poll for the arrival of
                     the initial search result via the method filled, and for
                     subsequent changes by comparing the output of method
                     getall against a saved copy, this is not the recommended
                     behaviour. Setting the -command callback and processing
                     the notifications as they arrive is much more efficient.

                     The command_prefix is called with two arguments, the type
                     of change, and the data of the change. The type is either
                     add or remove, indicating new data, or deleted data,
                     respectively.  The data of the change is always a
                     dictionary listing the added/removed names and their
                     associated data.

                     The first change reported for a search is always the set
                     of matching entries at the time of the search.

       Methods:

              $result destroy
                     Destroys the object and cancels any continuous monitoring
                     of the service the object may have had active.

              $result filled
                     The result is a boolean value indicating whether the
                     search result has already arrived (True), or not (False).

              $result get name
                     Returns the data associated with the given name at bind-
                     time.

              $result names
                     Returns a list containing all names known to the object
                     at the time of the invokation.

              $result size
                     Returns an integer value specifying the size of the
                     result at the time of the invokation.

              $result getall ?pattern?
                     Returns a dictionary containing the search result at the
                     time of the invokation, mapping the matching names to the
                     data associated with them at bind-time.

HISTORY
       0.3.1  Fixed SF Bug 1954771.

       0.3    Extended the client with the ability to perform asynchronous and
              continuous searches.

       0.2    Extended the client with the ability to generate events when it
              loses its connection to the name service. Based on package
              uevent.

       0.1    Initial implementation of the client.

BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will undoubtedly contain
       bugs and other problems.  Please report such in the category nameserv
       of the Tcllib SF Trackers
       [http://sourceforge.net/tracker/?group_id=12883].  Please also report
       any ideas for enhancements you may have for either package and/or
       documentation.

SEE ALSO
       nameserv::common(n), nameserv::server(n)

KEYWORDS
       client, name service

CATEGORY
       Networking

COPYRIGHT
       Copyright (c) 2007-2008 Andreas Kupries <andreas_kupries@users.sourceforge.net>




nns                                  0.4.2                         nameserv(n)
