dns(n) dns dns(n)

NAME
       dns - Tcl Domain Name Service Client

SYNOPSIS
       package require TTccll  88..22

       package require ddnnss  ??11..11??

       ::::ddnnss::::rreessoollvvee query ?options?

       ::::ddnnss::::ccoonnffiigguurree ?options?

       ::::ddnnss::::nnaammee token

       ::::ddnnss::::aaddddrreessss token

       ::::ddnnss::::ccnnaammee token

       ::::ddnnss::::rreessuulltt token

       ::::ddnnss::::ssttaattuuss token

       ::::ddnnss::::eerrrroorr token

       ::::ddnnss::::rreesseett token

       ::::ddnnss::::wwaaiitt token

       ::::ddnnss::::cclleeaannuupp token



DESCRIPTION
       The  dns  package  provides  a Tcl only Domain Name Service client. You
       should refer to  RFC  1034  (http://www.rfc-editor.org/rfc/rfc1034.txt)
       and  RFC  1035 (http://www.rfc-editor.org/rfc/rfc1035.txt) for informa-
       tion about the DNS protocol or read resolver(3) to find out how  the  C
       library  resolves  domain  names.   The intention of this package is to
       insulate Tcl scripts  from  problems  with  using  the  system  library
       resolver for slow name servers.  It may or may not be of practical use.
       Internet name resolution is a complex business and DNS is only one part
       of the resolver. You may find you are supposed to be using hosts files,
       NIS or WINS to name a few other systems. This package is not a  substi-
       tute  for the C library resolver - it does however implement name reso-
       lution over DNS.  The package also extends the package uurrii  to  support
       DNS    URIs   or   the   form   dns:what.host.com   or   dns://my.name-
       server/what.host.com. The ddnnss::::rreessoollvvee command can handle DNS  URIs  or
       simple domain names as a query.

       Note:  The  package  defaults to using DNS over TCP connections. If you
       wish to use UDP you will need to get the tcludp package and get a  ver-
       sion  that  correctly handles binary data (> 1.0.4).  This is available
       at http://tcludp.sourceforge.net/. If the udp package is  detected,  it
       will be used automatically.

CCOOMMMMAANNDDSS
       ::::ddnnss::::rreessoollvvee query ?options?
              Resolve  a  domain  name  using  the  DNS protocol. query is the
              domain name to be lookup up. This should be either a fully qual-
              ified domain name or a DNS URI.

              -nnaammeesseerrvveerr hostname or -sseerrvveerr hostname
                     Specify an alternative name server for this request.

              -pprroottooccooll tcp|udp
                     Specify the network protocol to use for this request. Can
                     be one of tcp or udp.

              -ppoorrtt portnum
                     Specify an alternative port.

              -sseeaarrcchh domainlist

              -ttiimmeeoouutt milliseconds
                     Override the default timeout.

              -ttyyppee TYPE
                     Specify the type of DNS record  you  are  interested  in.
                     Valid  values  are A, NS, MD, MF, CNAME, SOA, MB, MG, MR,
                     NULL, WKS, PTR, HINFO, MINFO, MX, TXT, SPF, AXFR,  MAILB,
                     MAILA  and  *.   See RFC1035 for details about the return
                     values.  See http://spf.pobox.com/ about SPF.

              -ccllaassss CLASS
                     Specify the class of domain name. This is usually IN  but
                     may be one of IN for internet domain names, CS, CH, HS or
                     * for any class.

              -rreeccuurrssee boolean
                     Set to false if you do not want the name server to recur-
                     sively act upon your request. Normally set to true.

              -ccoommmmaanndd procname
                     Set a procedure to be called upon request completion. The
                     procedure will be passed the token as its only  argument.


       ::::ddnnss::::ccoonnffiigguurree ?options?
              The  ::dns::configure  command is used to setup the dns package.
              The server to query, the protocol and domain search path are all
              set  via  this command. If no arguments are provided then a list
              of all the current settings is returned.  If only  one  argument
              then  it  must  the the name of an option and the value for that
              option is returned.

              -nnaammeesseerrvveerr hostname
                     Set the default name server to be used  by  all  queries.
                     The default is localhost.

              -pprroottooccooll tcp|udp
                     Set  the default network protocol to be used. Defaults to
                     tcp.

              -ppoorrtt portnum
                     Set the default port to  use  on  the  name  server.  The
                     default is 53.

              -sseeaarrcchh domainlist
                     Set the domain search list. This is currently not used.

              -ttiimmeeoouutt milliseconds
                     Set  the  default timeout value for DNS lookups. Defaults
                     to 30 seconds.


       ::::ddnnss::::nnaammee token
              Returns a list of all domain names returned as an answer to your
              query.


       ::::ddnnss::::aaddddrreessss token
              Returns a list of the address records that match your query.


       ::::ddnnss::::ccnnaammee token
              Returns  a  list  of canonical names (usually just one) matching
              your query.


       ::::ddnnss::::rreessuulltt token
              Returns a list of all the decoded answer  records  provided  for
              your  query.  This  permits  you  to extract the result for more
              unusual query types.


       ::::ddnnss::::ssttaattuuss token
              Returns the status flag. For a successfully completed query this
              will  be  ok.  May  be  error  or  timeout  or  eof.   See  also
              ::::ddnnss::::eerrrroorr


       ::::ddnnss::::eerrrroorr token
              Returns the error message provided for requests whose status  is
              error.   If  there  is  no error message then an empty string is
              returned.


       ::::ddnnss::::rreesseett token
              Reset or cancel a DNS query.


       ::::ddnnss::::wwaaiitt token
              Wait for a DNS query to complete and return the status upon com-
              pletion.


       ::::ddnnss::::cclleeaannuupp token
              Remove all state variables associated with the request.

EEXXAAMMPPLLEESS
       % set tok [dns::resolve www.tcl.tk]
       ::dns::1
       % dns::status $tok
       ok
       % dns::address $tok
       199.175.6.239
       % dns::name $tok
       www.tcl.tk
       % dns::cleanup $tok

       Using DNS URIs as queries:
       % set tok [dns::resolve "dns:tcl.tk;type=MX"]
       % set tok [dns::resolve "dns://l.root-servers.net/www.tcl.tk"]

       Reverse address lookup:
       % set tok [dns::resolve 127.0.0.1]
       ::dns::1
       % dns::name $tok
       localhost
       % dns::cleanup $tok

AUTHORS       Pat Thoyts

SEE ALSO
       resolver(5)

KKEEYYWWOORRDDSS
       DNS, domain name service, resolver, rfc 1034, rfc 1035

COPYRIGHT       Copyright (c) 2002, Pat Thoyts



dns                                   1.1                               dns(n)