adns
                                       
   Advanced, easy to use, asynchronous-capable DNS client library.
   
   adns is a resolver library for C (and C++) programs. In contrast with
   the existing interfaces, gethostbyname et al and libresolv, it has the
   following features:
     * It is reasonably easy to use for simple programs which just want
       to translate names to addresses, look up MX records, etc.
     * It can be used in an asynchronous, non-blocking, manner. Many
       queries can be handled simultaneously.
     * Responses are decoded automatically into a natural representation
       for a C program - there is no need to deal with DNS packet
       formats.
     * Sanity checking (eg, name syntax checking, reverse/forward
       correspondence, CNAME pointing to CNAME) is performed
       automatically.
     * Time-to-live, CNAME and other similar information is returned in
       an easy-to-use form, without getting in the way.
     * There is no global state in the library; resolver state is an
       opaque data structure which the client creates explicitly. A
       program can have several instances of the resolver.
     * Errors are reported to the application in a way that distinguishes
       the various causes of failure properly.
     * Understands conventional resolv.conf, but this can overridden by
       environment variables.
     * Flexibility. For example, the application can tell adns to: ignore
       environment variables (for setuid programs), disable sanity checks
       eg to return arbitrary data, override or ignore resolv.conf in
       favour of supplied configuration, etc.
     * Believed to be correct ! For example, will correctly back off to
       TCP in case of long replies or queries, or to other nameservers if
       several are available. It has sensible handling of bad responses
       etc.
       
Forthcoming:

   I hope that future versions may also have the following features:
     * The library will be useable by threads in a multithreaded program
       in a natural way. It will multiplex many threads' queries through
       a single query socket.
     * Limited caching behaviour.
     * IPv6 support.
       
   (Technical note: adns requires a real nameserver like BIND running on
   the same system or a nearby one, which must be willing to provide
   `recursive service'. I.e., adns is a `stub resolver'. All properly
   configured UN*X and GNU systems will already have such nameserver(s);
   they are usually listed in /etc/resolv.conf.)
   
Feedback

   If you are subscribed to adns-discuss please send bug reports there;
   otherwise mail them to adns-bugreports@chiark.greenend.org.uk.
   
Mailinglists

   I have set up mailinglists adns-announce and adns-discuss. The
   announcements list is moderated and will contain only announcements of
   important bugs, new versions, &c. The bug reports address mentioned
   above is also a mailing list; feel free to subscribe to it.
   
   There are [1]archives and subscription web pages, or you can subscribe
   by sending mail containing the word `subscribe' to
   adns-announce-REQUEST@chiark.greenend.org.uk or
   adns-discuss-REQUEST@chiark.greenend.org.uk.
   
Download

   Available for download from [2]chiark.greenend.org.uk are:
     * The [3]current pre-release version as a gzipped tarfile.
     * All released versions are also available via [4]anonymous FTP.
       
   adns is also available from the GNU Project FTP servers and their
   mirrors.
   
Copyright and licensing

   adns is Copyright 1997-1999 Ian Jackson.
   
   adns is free software; you can redistribute it and/or modify it under
   the terms of the GNU General Public License as published by the Free
   Software Foundation; either version 2 of the License, or (at your
   option) any later version.
   
   This program and documentation is distributed in the hope that it will
   be useful, but without any warranty; without even the implied warranty
   of merchantability or fitness for a particular purpose. See the [5]GNU
   General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with adns, or one should be available above; if not, write to
   the [6]Free Software Foundation, 59 Temple Place - Suite 330, Boston,
   MA 02111-1307, USA, or email adns-maint@chiark.greenend.org.uk.
     _________________________________________________________________
   
   [7]Ian Jackson / [8]adns-maint@chiark.greenend.org.uk; more [9]free
   software by me.
   
   [10]GNU home page; [11]site or mirror home page
   
   This web page is Copyright (C)1996-1999 Ian Jackson. See the
   [12]Copyright/acknowledgements.
   
   Use any browser - [13]Campaign for a non-browser-specific WWW

References

   1. http://www.chiark.greenend.org.uk/mailman/listinfo
   2. http://www.chiark.greenend.org.uk/
   3. http://www.chiark.greenend.org.uk/~ian/adns/adns.tar.gz
   4. ftp://ftp.chiark.greenend.org.uk/users/ian/userv/
   5. http://www.chiark.greenend.org.uk/~ian/COPYING.txt
   6. http://www.fsf.org/
   7. http://www.chiark.greenend.org.uk/
   8. mailto:adns-maint@chiark.greenend.org.uk
   9. http://www.chiark.greenend.org.uk/~ian/software/
  10. http://www.gnu.org/
  11. http://www.chiark.greenend.org.uk/
  12. http://www.chiark.greenend.org.uk/~ian/sw-www-copy.html
  13. http://www.anybrowser.org/campaign/