<?xml version='1.0' encoding='UTF-8' standalone='no'?>
<doxygen xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="compound.xsd" version="1.8.16">
<compounddef id="group__dns" kind="group">
<compoundname>dns</compoundname>
<title>DNS</title>
<briefdescription>
</briefdescription>
<detaileddescription>
<para>Implements a DNS host name to IP address resolver.</para>
<para>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.</para>
<para>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.</para>
<para>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).</para>
<para>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!</para>
<para>All functions must be called from TCPIP thread.</para>
<para><simplesect kind="see"><para><ref refid="group__netconn__common" kindref="compound">Common functions</ref> for thread-safe <ref refid="gen__calls_8c_1a5e545f93bf6f37890415be1fc90815dd" kindref="member">access</ref>. </para>
</simplesect>
</para>
</detaileddescription>
</compounddef>
</doxygen>
