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 <span id="projectnumber">2.0</span>
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<p>Implements a DNS host name to IP address resolver.</p>
<p>The lwIP DNS resolver functions are used to lookup a host name and map it to a numerical IP address. It maintains a list of resolved hostnames that can be queried with the dns_lookup() function. New hostnames can be resolved using the dns_query() function.</p>
<p>The lwIP version of the resolver also adds a non-blocking version of gethostbyname() that will work with a raw API application. This function checks for an IP address string first and converts it if it is valid. gethostbyname() then does a dns_lookup() to see if the name is already in the table. If so, the IP is returned. If not, a query is issued and the function returns with a ERR_INPROGRESS status. The app using the dns client must then go into a waiting state.</p>
<p>Once a hostname has been resolved (or found to be non-existent), the resolver code calls a specified callback function (which must be implemented by the module that uses the resolver).</p>
<p>Multicast DNS queries are supported for names ending on ".local". However, only "One-Shot Multicast DNS Queries" are supported (RFC 6762 chapter 5.1), this is not a fully compliant implementation of continuous mDNS querying!</p>
<p>All functions must be called from TCPIP thread.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="../../d4/de2/group__netconn__common.html">Common functions</a> for thread-safe <a class="el" href="../../d3/d0a/gen__calls_8c.html#a5e545f93bf6f37890415be1fc90815dd">access</a>. </dd></dl>
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