Provided by: tcllib_1.14-dfsg-1_all bug

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(3tcl), nameserv::server(3tcl)

KEYWORDS

       client, name service

CATEGORY

       Networking

COPYRIGHT

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