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nns_intro(3tcl) Name service facility nns_intro(3tcl) 





NAME


nns_intro - Name service facility, introduction






DESCRIPTION


nns (short for nano nameservice) is a facility built
    for the package comm, adding a simple name service to it. It is also
    built on top of comm, using it for the exchange of messages between
    the client and server parts.


This name service facility has nothing to do with the Internet's
    Domain Name System, otherwise known as DNS. If the reader is
    looking for a package dealing with that please see either of the packages
    dns and resolv, both found in Tcllib too.


Tcllib provides 2 applications and 4 packages which are working
    together and provide access to the facility at different levels.






APPLICATIONS


The application nnsd provides a simple name server which
    can be run by anybody anywhere on their system, as they see fit. It is also
    an example on the use of the server-side package
  nameserv::server.


Complementing this server is the nns client application. A
    possible, but no very sensible use would be to enter name/port bindings into
    a server from a shell script. Not sensible, as shell scripts normally do not
    provide a comm-based service.


The only case for this to make some sense would be in a shell
    script wrapped around a Tcl script FOO which is using comm, to register the
    listening port used by FOO. However even there it would much more sensible
    to extend FOO to use the nameservice directly. And in regard on how to that
    nns can be used as both example and template. Beyond that it may also
    be useful to perform nameservice queries from shell scripts.


The third application, nnslog is a stripped down form of
    the nns client application. It is reduced to perform a continuous
    search for all changes and logs all received events to stdout.


Both clients use the nameserv::auto package to
    automatically hande the loss and restoration of the connection to the
    server.






PACKAGES


The two main packages implementing the service are nameserv
    and nameserv::server, i.e. client and server. The latter has not much
    of an API, just enough to start, stop, and configure it. See the application
    nnsd on how to use it.


The basic client, in package nameserv, provides the main
    API to manipulate and query the service. An example of its use is the
    application nns.


The second client package, nameserv::auto is API compatible
    to the basic client, but provides the additional functionality that it will
    automatically restore data like bound names when the connection to the name
    service was lost and then reestablished. I.e. it automatically detects the
    loss of the server and re-enters the data when the server comes back.


The package nameserv::common is of no interest to users. It
    is an internal package containing code and definitions common to the
    packages nameserv and nameserv::server.


All packages use the uevent package for the reporting of
    special circumstances via events, and reserve the uevent-tag nameserv
    for their exclusive use. All their events will be posted to that tag.






INTERNALS


The document Name service facility, client/server protocol
    specifies the protocol used by the packages nameserv and
    nameserv::server to talk to each other. It is of no interest to users
    of either the packages or applications.


Developers wishing to modify and/or extend or to just understand
    the internals of the nameservice facility however are strongly advised to
    read it.






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(3tcl), nameserv::auto(3tcl), nameserv::common(3tcl),
    nameserv::protocol(3tcl), nameserv::server(3tcl), nnsd(3tcl), nss(3tcl)






KEYWORDS


client, name service, server






CATEGORY


Networking






COPYRIGHT


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








  

    1.0
    tcllib