dns(n)									dns								    dns(n)

NAME

       dns - Tcl Domain Name Service Client

SYNOPSIS

       package require Tcl 8.2

       package require dns ?1.0.1?

       ::dns::resolve query ?options?

       ::dns::configure ?options?

       ::dns::name token

       ::dns::address token

       ::dns::cname token

       ::dns::status token

       ::dns::error token

       ::dns::reset token

       ::dns::wait token

       ::dns::cleanup token

DESCRIPTION

       The  dns  package  provides  a Tcl only Domain Name Service client. You should refer to RFC 1034 and RFC 1035 for information 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.  The package also
       extends the package uri to support DNS URIs or the form dns:what.host.com or dns://my.nameserver/what.host.com.	The  dns::resolve  command
       can handle DNS URIs or simple domain names as a query.

       Note:  This  package  uses TCP to query DNS servers as the tcl core does not implement UDP networking. This means that this module will not
       work if DNS over TCP is blocked by a firewall, or not accepted by the chosen nameserver.

COMMANDS

       ::dns::resolve 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  qualified
	      domain name or a DNS URI.

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

	      -protocol tcp|udp
		     Specify  the network protocol to use for this request. Can be one of tcp or udp. However only tcp is currently implemented in
		     the package.

	      -port portnum
		     Specify an alternative port.

	      -search domainlist

	      -timeout milliseconds
		     Override the default timeout.

	      -type 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, AXFR, MAILB, MAILA and *. See RFC1035 for details about the return values.

	      -class 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.

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

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

       ::dns::configure ?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.

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

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

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

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

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

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

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

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

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

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

       ::dns::reset token
	      Reset or cancel a DNS query.

       ::dns::wait token
	      Wait for a DNS query to complete and return the status upon completion.

       ::dns::cleanup token
	      Remove all state variables associated with the request.

EXAMPLES

       % 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

       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"]

SEE ALSO

       resolver(5)

AUTHORS

       Pat Thoyts

KEYWORDS

       DNS, resolver, domain name service

dns								       1.0.1								    dns(n)