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[comment {-*- tcl -*- doctools manpage}]
[manpage_begin nns_intro n 1.0]
[see_also nameserv(n)]
[see_also nameserv::auto(n)]
[see_also nameserv::common(n)]
[see_also nameserv::protocol(n)]
[see_also nameserv::server(n)]
[see_also nnsd(n)]
[see_also nss(n)]
[keywords client]
[keywords {name service}]
[keywords server]
[copyright {2008 Andreas Kupries <andreas_kupries@users.sourceforge.net>}]
[moddesc {Name service facility}]
[titledesc {Name service facility, introduction}]
[category Networking]
[description]
[para]
[term nns] (short for [emph {nano nameservice}]) is a facility built
for the package [package comm], adding a simple name service to it.
It is also built on top of [package comm], using it for the exchange
of messages between the client and server parts.
[para]
This name service facility has nothing to do with the Internet's
[term {Domain Name System}], otherwise known as [term DNS]. If the
reader is looking for a package dealing with that please see either of
the packages [package dns] and [package resolv], both found in Tcllib
too.
[para]
Tcllib provides 2 applications and 4 packages which are working
together and provide access to the facility at different levels.
[section Applications]
The application [syscmd 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
[package nameserv::server].
[para]
Complementing this server is the [syscmd 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 [package comm]-based service.
[para]
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 [syscmd nns]
can be used as both example and template.
Beyond that it may also be useful to perform nameservice queries from
shell scripts.
[para]
The third application, [syscmd nnslog] is a stripped down form of the
[syscmd nns] client application. It is reduced to perform a continuous
search for all changes and logs all received events to stdout.
[para]
Both clients use the [package nameserv::auto] package to automatically
hande the loss and restoration of the connection to the server.
[section Packages]
The two main packages implementing the service are [package nameserv]
and [package 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 [syscmd nnsd] on how to use it.
[para]
The basic client, in package [package nameserv], provides the main API
to manipulate and query the service. An example of its use is the
application [syscmd nns].
[para]
The second client package, [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.
[para]
The package [package nameserv::common] is of no interest to users. It
is an internal package containing code and definitions common to the
packages [package nameserv] and [package nameserv::server].
[para]
All packages use the [package uevent] package for the reporting of
special circumstances via events, and reserve the uevent-tag
[term nameserv] for their exclusive use. All their events will be
posted to that tag.
[section Internals]
The document [term {Name service facility, client/server protocol}]
specifies the protocol used by the packages [package nameserv] and
[package nameserv::server] to talk to each other. It is of no interest
to users of either the packages or applications.
[para]
Developers wishing to modify and/or extend or to just understand the
internals of the nameservice facility however are strongly advised to
read it.
[vset CATEGORY nameserv]
[include ../common-text/feedback.inc]
[manpage_end]
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