1This is ares, an asynchronous resolver library.  It is intended for
2applications which need to perform DNS queries without blocking, or
3need to perform multiple DNS queries in parallel.  The primary
4examples of such applications are servers which communicate with
5multiple clients and programs with graphical user interfaces.
6
7This library implementation is not especially portable to crufty old
8systems like SunOS 4.  It assumes a compiler which can handle ANSI C
9syntax, a system malloc which properly handles realloc(NULL, foo) and
10free(NULL), and a reasonably up-to-date <arpa/nameser.h>.
11
12I have attempted to preserve the externally visible behavior of the
13BIND resolver in nearly all respects.  The API of the library is, of
14course, very different from the synchronous BIND API; instead of
15invoking a function like res_send() and getting a return value back
16indicating the number of bytes in the response, you invoke a function
17like ares_send() and give it a callback function to invoke when the
18response arrives.  You then have to select() on the file descriptors
19indicated by ares_fds(), with a timeout given by ares_timeout().  You
20call ares_process() when select() returns.
21
22Some features are missing from the current version of ares, relative
23to the BIND resolver:
24
25	* There is no IPV6 support.
26	* There is no hostname verification.
27	* There is no logging of unexpected events.
28	* There is no debugging-oriented logging.
29	* There is no YP support.
30
31libares requires an ANSI compiler to compile and use.  To build the
32library, just run "./configure" and "make".  To install it, run "make
33install".  Run "./configure --help" to see a list of options you can
34provide to configure to change how the library builds.  libares has no
35data files, so you can move the include file and library around freely
36without leaving behind any dependencies on old paths.  Building the
37library will also build the "adig" program, a little toy for trying
38out the library.  It doesn't get installed.
39
40libares is distributed at athena-dist.mit.edu:pub/ATHENA/ares.  Please
41send bug reports and comments to ghudson@mit.edu.
42