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nameserv(n) Name service facility nameserv(n) 





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

  







  

  

  

  

  
  

  

  

  

  










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.



  

  

  

  

  

  

  

  

  

  




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:



  

  
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.

  

  
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:



  

  







  

  
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.

  







  

  







  
$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 Trackers
    [http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for
    enhancements you may have for either package and/or documentation.


When proposing code changes, please provide unified diffs,
    i.e the output of diff -u.


Note further that attachments are strongly preferred over
    inlined patches. Attachments can be made by going to the Edit form of
    the ticket immediately after its creation, and then using the left-most
    button in the secondary navigation bar.






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>








  

    0.4.2
    tcllib