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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>15&nbsp;DNS: Domain Name Service Queries</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,&quot;tocview_0&quot;);">&#9660;</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x">Net:<span class="mywbr"> &nbsp;</span> Networking Libraries</a></td></tr></table></div><div class="tocviewsublisttop" style="display: block;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1&nbsp;</td><td><a href="http-client.html" class="tocviewlink" data-pltdoc="x">HTTP Client</a></td></tr><tr><td align="right">2&nbsp;</td><td><a href="url.html" class="tocviewlink" data-pltdoc="x">URLs and HTTP</a></td></tr><tr><td align="right">3&nbsp;</td><td><a href="uri-codec.html" class="tocviewlink" data-pltdoc="x">URI Codec:<span class="mywbr"> &nbsp;</span> Encoding and Decoding URIs</a></td></tr><tr><td align="right">4&nbsp;</td><td><a href="websocket.html" class="tocviewlink" data-pltdoc="x">Web<span class="mywbr"> &nbsp;</span>Socket</a></td></tr><tr><td align="right">5&nbsp;</td><td><a href="ftp.html" class="tocviewlink" data-pltdoc="x">FTP:<span class="mywbr"> &nbsp;</span> Client</a></td></tr><tr><td align="right">6&nbsp;</td><td><a href="sendurl.html" class="tocviewlink" data-pltdoc="x">Send URL:<span class="mywbr"> &nbsp;</span> Opening a Web Browser</a></td></tr><tr><td align="right">7&nbsp;</td><td><a href="smtp.html" class="tocviewlink" data-pltdoc="x">SMTP:<span class="mywbr"> &nbsp;</span> Sending E-<wbr></wbr>Mail</a></td></tr><tr><td align="right">8&nbsp;</td><td><a href="sendmail.html" class="tocviewlink" data-pltdoc="x"><span class="stt">sendmail</span>:<span class="mywbr"> &nbsp;</span> Sending E-<wbr></wbr>Mail</a></td></tr><tr><td align="right">9&nbsp;</td><td><a href="head.html" class="tocviewlink" data-pltdoc="x">Headers:<span class="mywbr"> &nbsp;</span> Parsing and Constructing</a></td></tr><tr><td align="right">10&nbsp;</td><td><a href="imap.html" class="tocviewlink" data-pltdoc="x">IMAP:<span class="mywbr"> &nbsp;</span> Reading Mail</a></td></tr><tr><td align="right">11&nbsp;</td><td><a href="pop3.html" class="tocviewlink" data-pltdoc="x">POP3:<span class="mywbr"> &nbsp;</span> Reading Mail</a></td></tr><tr><td align="right">12&nbsp;</td><td><a href="mime.html" class="tocviewlink" data-pltdoc="x">MIME:<span class="mywbr"> &nbsp;</span> Decoding Internet Data</a></td></tr><tr><td align="right">13&nbsp;</td><td><a href="base64.html" class="tocviewlink" data-pltdoc="x">Base 64:<span class="mywbr"> &nbsp;</span> Encoding and Decoding</a></td></tr><tr><td align="right">14&nbsp;</td><td><a href="qp.html" class="tocviewlink" data-pltdoc="x">Quoted-<wbr></wbr>Printable:<span class="mywbr"> &nbsp;</span> Encoding and Decoding</a></td></tr><tr><td align="right">15&nbsp;</td><td><a href="" class="tocviewselflink" data-pltdoc="x">DNS:<span class="mywbr"> &nbsp;</span> Domain Name Service Queries</a></td></tr><tr><td align="right">16&nbsp;</td><td><a href="nntp.html" class="tocviewlink" data-pltdoc="x">NNTP:<span class="mywbr"> &nbsp;</span> Newsgroup Protocol</a></td></tr><tr><td align="right">17&nbsp;</td><td><a href="tcp.html" class="tocviewlink" data-pltdoc="x">TCP:<span class="mywbr"> &nbsp;</span> Unit and Signature</a></td></tr><tr><td align="right">18&nbsp;</td><td><a href="tcp-redirect.html" class="tocviewlink" data-pltdoc="x">TCP Redirect:<span class="mywbr"> &nbsp;</span> <span class="RktSym"><span class="RktStxLink">tcp^</span></span> via Channels</a></td></tr><tr><td align="right">19&nbsp;</td><td><a href="ssl-tcp-unit.html" class="tocviewlink" data-pltdoc="x">SSL Unit:<span class="mywbr"> &nbsp;</span> <span class="RktSym"><span class="RktStxLink">tcp^</span></span> via SSL</a></td></tr><tr><td align="right">20&nbsp;</td><td><a href="cgi.html" class="tocviewlink" data-pltdoc="x">CGI Scripts</a></td></tr><tr><td align="right">21&nbsp;</td><td><a href="cookie.html" class="tocviewlink" data-pltdoc="x">Cookie:<span class="mywbr"> &nbsp;</span> HTTP Client Storage</a></td></tr><tr><td align="right"></td><td><a href="doc-bibliography.html" class="tocviewlink" data-pltdoc="x">Bibliography</a></td></tr><tr><td align="right"></td><td><a href="doc-index.html" class="tocviewlink" data-pltdoc="x">Index</a></td></tr></table></div></div><div class="tocviewlist"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,&quot;tocview_1&quot;);">&#9658;</a></td><td>15&nbsp;</td><td><a href="" class="tocviewselflink" data-pltdoc="x">DNS:<span class="mywbr"> &nbsp;</span> Domain Name Service Queries</a></td></tr></table><div class="tocviewsublistbottom" style="display: none;" id="tocview_1"><table cellspacing="0" cellpadding="0"><tr><td align="right">15.1&nbsp;</td><td><a href="#%28part._dns-proc%29" class="tocviewlink" data-pltdoc="x">Functions</a></td></tr><tr><td align="right">15.2&nbsp;</td><td><a href="#%28part._.D.N.S_.Unit%29" class="tocviewlink" data-pltdoc="x">DNS Unit</a></td></tr><tr><td align="right">15.3&nbsp;</td><td><a href="#%28part._.D.N.S_.Signature%29" class="tocviewlink" data-pltdoc="x">DNS Signature</a></td></tr></table></div></div></div><div class="tocsub"><div class="tocsubtitle">On this page:</div><table class="tocsublist" cellspacing="0"><tr><td><span class="tocsublinknumber">15.1<tt>&nbsp;</tt></span><a href="#%28part._dns-proc%29" class="tocsubseclink" data-pltdoc="x">Functions</a></td></tr><tr><td><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-get-address%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">dns-<wbr></wbr>get-<wbr></wbr>address</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-get-name%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">dns-<wbr></wbr>get-<wbr></wbr>name</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-get-mail-exchanger%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">dns-<wbr></wbr>get-<wbr></wbr>mail-<wbr></wbr>exchanger</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-find-nameserver%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">dns-<wbr></wbr>find-<wbr></wbr>nameserver</span></span></a></td></tr><tr><td><span class="tocsublinknumber">15.2<tt>&nbsp;</tt></span><a href="#%28part._.D.N.S_.Unit%29" class="tocsubseclink" data-pltdoc="x">DNS Unit</a></td></tr><tr><td><a href="#%28def._%28%28lib._net%2Fdns-unit..rkt%29._dns~40%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">dns@</span></span></a></td></tr><tr><td><span class="tocsublinknumber">15.3<tt>&nbsp;</tt></span><a href="#%28part._.D.N.S_.Signature%29" class="tocsubseclink" data-pltdoc="x">DNS Signature</a></td></tr><tr><td><a href="#%28form._%28%28lib._net%2Fdns-sig..rkt%29._dns~5e%29%29" class="tocsubnonseclink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">dns^</span></span></a></td></tr></table></div></div><div class="maincolumn"><div class="main"><div class="navsettop"><span class="navleft"><form class="searchform"><input class="searchbox" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, &quot;6.1&quot;, &quot;../&quot;);" onfocus="this.style.color=&quot;black&quot;; this.style.textAlign=&quot;left&quot;; if (this.value == &quot;...search manuals...&quot;) this.value=&quot;&quot;;" onblur="if (this.value.match(/^ *$/)) { this.style.color=&quot;#888&quot;; this.style.textAlign=&quot;center&quot;; this.value=&quot;...search manuals...&quot;; }"/></form>&nbsp;&nbsp;<a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot(&quot;6.1&quot;);">top</a></span><span class="navright">&nbsp;&nbsp;<a href="qp.html" title="backward to &quot;14 Quoted-Printable: Encoding and Decoding&quot;" data-pltdoc="x">&larr; prev</a>&nbsp;&nbsp;<a href="index.html" title="up to &quot;Net: Networking Libraries&quot;" data-pltdoc="x">up</a>&nbsp;&nbsp;<a href="nntp.html" title="forward to &quot;16 NNTP: Newsgroup Protocol&quot;" data-pltdoc="x">next &rarr;</a></span>&nbsp;</div><h3 x-source-module="(lib &quot;net/scribblings/net.scrbl&quot;)" x-part-tag="&quot;dns&quot;">15<tt>&nbsp;</tt><a name="(part._dns)"></a><a name="(mod-path._net/dns)"></a>DNS: Domain Name Service Queries</h3><p><div class="SIntrapara"><table cellspacing="0" cellpadding="0" class="defmodule"><tr><td align="left"><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="stt"> </span><a href="" class="RktModLink" data-pltdoc="x"><span class="RktSym">net/dns</span></a><span class="RktPn">)</span></td><td align="right"><span class="RpackageSpec"><span class="Smaller">&nbsp;package:</span> <span class="stt">net-lib</span></span></td></tr></table></div><div class="SIntrapara">The <a href="" class="RktModLink" data-pltdoc="x"><span class="RktSym">net/dns</span></a> library provides
utilities for looking up hostnames.</div><div class="SIntrapara">Thanks to Eduardo Cavazos and Jason Crowe for repairs and
improvements.</div></p><h4 x-source-module="(lib &quot;net/scribblings/net.scrbl&quot;)" x-part-tag="&quot;dns-proc&quot;">15.1<tt>&nbsp;</tt><a name="(part._dns-proc)"></a>Functions</h4><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><table cellspacing="0" cellpadding="0" class="prototype RForeground"><tr><td><span class="RktPn">(</span><a name="(def._((lib._net/dns..rkt)._dns-get-address))"></a><span title="Provided from: net/dns | Package: net-lib"><span class="RktSym"><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-get-address%29%29" class="RktValDef RktValLink" data-pltdoc="x">dns-get-address</a></span></span></td><td><span class="hspace">&nbsp;</span></td><td><span class="RktVar">nameserver</span></td><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span></td></tr><tr><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span></td><td><span class="RktVar">address</span></td><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span></td></tr><tr><td><span class="hspace">&nbsp;</span></td><td><span class="hspace">&nbsp;</span>[</td><td><span class="RktPn">#:ipv6?</span><span class="hspace">&nbsp;</span><span class="RktVar">ipv6?</span>]<span class="RktPn">)</span></td><td><span class="hspace">&nbsp;</span></td><td>&rarr;</td><td><span class="hspace">&nbsp;</span></td><td><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></td></tr></table></blockquote></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">nameserver</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">address</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">ipv6?</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=data-structure-contracts.html%23%2528def._%2528%2528lib._racket%252Fcontract%252Fprivate%252Fmisc..rkt%2529._any%252Fc%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">any/c</a></span><span class="hspace">&nbsp;</span>=<span class="hspace">&nbsp;</span><span class="RktVal">#f</span></td></tr></table></blockquote></div><div class="SIntrapara">Consults the specified nameserver (normally a numerical address like
<span class="RktVal">"128.42.1.30"</span>) to obtain a numerical address for the given
Internet address.</div></p><p>The query record sent to the DNS server includes the "recursive" bit,
but <span class="RktSym"><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-get-address%29%29" class="RktValLink" data-pltdoc="x">dns-get-address</a></span> also implements a recursive search itself
in case the server does not provide this optional feature.</p><p>If <span class="RktVar">ipv6?</span> is a true value, then the numerical address
that is returned will be an IPv6 address. If no AAAA record exists,
an error will be raised.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._net/dns..rkt)._dns-get-name))"></a><span title="Provided from: net/dns | Package: net-lib"><span class="RktSym"><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-get-name%29%29" class="RktValDef RktValLink" data-pltdoc="x">dns-get-name</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">nameserver</span><span class="hspace">&nbsp;</span><span class="RktVar">address</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span>&rarr;<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></p></blockquote></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">nameserver</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">address</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Consults the specified nameserver (normally a numerical address like
<span class="RktVal">"128.42.1.30"</span>) to obtain a name for the given numerical
address.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._net/dns..rkt)._dns-get-mail-exchanger))"></a><span title="Provided from: net/dns | Package: net-lib"><span class="RktSym"><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-get-mail-exchanger%29%29" class="RktValDef RktValLink" data-pltdoc="x">dns-get-mail-exchanger</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">nameserver</span><span class="hspace">&nbsp;</span><span class="RktVar">address</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span>&rarr;<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></p></blockquote></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">nameserver</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">address</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Consults the specified nameserver to obtain the address for a mail
exchanger the given mail host address. For example, the mail exchanger
for <span class="RktVal">"ollie.cs.rice.edu"</span> might be <span class="RktVal">"cs.rice.edu"</span>.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((lib._net/dns..rkt)._dns-find-nameserver))"></a><span title="Provided from: net/dns | Package: net-lib"><span class="RktSym"><a href="#%28def._%28%28lib._net%2Fdns..rkt%29._dns-find-nameserver%29%29" class="RktValDef RktValLink" data-pltdoc="x">dns-find-nameserver</a></span></span><span class="RktPn"></span><span class="RktPn">)</span><span class="hspace">&nbsp;</span>&rarr;<span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=data-structure-contracts.html%23%2528def._%2528%2528lib._racket%252Fcontract%252Fbase..rkt%2529._or%252Fc%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">or/c</a></span><span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3f%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">string?</a></span><span class="hspace">&nbsp;</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=data-structure-contracts.html%23%2528def._%2528%2528lib._racket%252Fcontract%252Fprivate%252Fmisc..rkt%2529._false%252Fc%2529%2529&amp;version=6.1" class="RktValLink Sq" data-pltdoc="x">false/c</a></span><span class="RktPn">)</span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara">Attempts to find the address of a nameserver on the present system.
On Unix and Mac OS X, this procedure parses <span class="stt">"/etc/resolv.conf"</span> to
extract the first nameserver address. On Windows, it runs
<span class="stt">nslookup.exe</span>.</div></p><h4 x-source-module="(lib &quot;net/scribblings/net.scrbl&quot;)" x-part-tag="&quot;DNS_Unit&quot;">15.2<tt>&nbsp;</tt><a name="(part._.D.N.S_.Unit)"></a><a name="(mod-path._net/dns-unit)"></a>DNS Unit</h4><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p><span class="RktSym"><a href="#%28def._%28%28lib._net%2Fdns-unit..rkt%29._dns~40%29%29" class="RktValLink" data-pltdoc="x">dns@</a></span> and <span class="RktSym"><a href="#%28form._%28%28lib._net%2Fdns-sig..rkt%29._dns~5e%29%29" class="RktStxLink" data-pltdoc="x">dns^</a></span> are deprecated.
They exist for backward-compatibility and will likely be removed in
the future. New code should use the <a href="" class="RktModLink" data-pltdoc="x"><span class="RktSym">net/dns</span></a> module.</p></blockquote></blockquote></blockquote><p><table cellspacing="0" cellpadding="0" class="defmodule"><tr><td align="left"><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="stt"> </span><a href="#%28mod-path._net%2Fdns-unit%29" class="RktModLink" data-pltdoc="x"><span class="RktSym">net/dns-unit</span></a><span class="RktPn">)</span></td><td align="right"><span class="RpackageSpec"><span class="Smaller">&nbsp;package:</span> <span class="stt">compatibility-lib</span></span></td></tr></table></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>value</p></div></div><p class="RForeground"><a name="(def._((lib._net/dns-unit..rkt)._dns~40))"></a><span title="Provided from: net/dns-unit | Package: compatibility-lib"><span class="RktSym"><a href="#%28def._%28%28lib._net%2Fdns-unit..rkt%29._dns~40%29%29" class="RktValDef RktValLink" data-pltdoc="x">dns@</a></span></span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym">unit?</span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara">Imports nothing, exports <span class="RktSym"><a href="#%28form._%28%28lib._net%2Fdns-sig..rkt%29._dns~5e%29%29" class="RktStxLink" data-pltdoc="x">dns^</a></span>.</div></p><h4 x-source-module="(lib &quot;net/scribblings/net.scrbl&quot;)" x-part-tag="&quot;DNS_Signature&quot;">15.3<tt>&nbsp;</tt><a name="(part._.D.N.S_.Signature)"></a><a name="(mod-path._net/dns-sig)"></a>DNS Signature</h4><p><table cellspacing="0" cellpadding="0" class="defmodule"><tr><td align="left"><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&amp;rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&amp;version=6.1" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="stt"> </span><a href="#%28mod-path._net%2Fdns-sig%29" class="RktModLink" data-pltdoc="x"><span class="RktSym">net/dns-sig</span></a><span class="RktPn">)</span></td><td align="right"><span class="RpackageSpec"><span class="Smaller">&nbsp;package:</span> <span class="stt">compatibility-lib</span></span></td></tr></table></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>signature</p></div></div><p class="RForeground"><a name="(form._((lib._net/dns-sig..rkt)._dns~5e))"></a><span title="Provided from: net/dns-sig | Package: compatibility-lib"><span class="RktSym"><a href="#%28form._%28%28lib._net%2Fdns-sig..rkt%29._dns~5e%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">dns^</a></span></span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span>signature</p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"><blockquote class="leftindent"></blockquote></div></p><p>Includes everything exported by the <a href="" class="RktModLink" data-pltdoc="x"><span class="RktSym">net/dns</span></a> module.</p><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, &quot;6.1&quot;, &quot;../&quot;);" onfocus="this.style.color=&quot;black&quot;; 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