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dns(n)					       dns					   dns(n)

       dns - Tcl Domain Name Service Client

       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

       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.

       ::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,
		     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

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

	      -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.

       % set tok [dns::resolve www.tcl.tk]
       % dns::status $tok
       % dns::address $tok
       % dns::name $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"]


       Pat Thoyts

       DNS, resolver, domain name service

dns					      1.0.1					   dns(n)
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