--- name: "nns_intro" section: "3tcl" platform: "linux" package: "tcllib" version: "2.0+dfsg-4" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/nns_intro" --- # nns\_intro(3tcl) Name service facility, introduction ``` ``` ## 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)](/nnsd/3tcl.md), nss(3tcl) ## KEYWORDS client, name service, server ## CATEGORY Networking ## COPYRIGHT ``` Copyright (c) 2008 Andreas Kupries ```