(Perl) Revert to Default DNS Nameservers

See more DNS Examples

Demonstrates how to revert back to the default nameservers of the local system where your application is running.

Note: This example requires Chilkat v9.5.0.96 or later.

Chilkat Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux, Solaris

use chilkat();

# The only reason you would have to revert back to the local system's default nameservers
# is if your application had previously set different nameservers, and you wish to revert back.

# When your application starts, the DNS nameservers to be used are the default nameservers
# configured on the system where your application is running.

# There is one exception: Chilkat defaults to using the public Google nameservers (8.8.8.8 and 8.8.4.4) for
# Android applications. Reverting to the default nameservers would revert to the Google nameservers.

# However, Chilkat does not query the local system for the default nameservers unless Chilkat needs
# to do a DNS lookup and there not yet any DNS nameservers defined.  Thus technically, when your application
# starts, there are no default nameservers. They are auto-assigned when first needed.

# If your application explicitly defines DNS nameservers, such as by calling AddDefaultnamervers, or AddNameserver
# then Chilkat will not automatically auto-assign.

$dns = chilkat::CkDns->new();

# Here we are explicitly adding the system default nameservers, because technically this application
# has not yet done anything that would require a DNS lookup, and thus DNS nameservers are not yet defined.
# Your default nameserver is assumed to not support TLS.
$dns->AddDefaultNameservers();

# Let's examine our nameservers
$nsCount = $dns->get_NumNameservers();
$i = 0;
while ($i < $nsCount) {
    print ($i + 1) . ": " . $dns->getNameserver($i) . "\r\n";
    $i = $i + 1;
}

# On my Windows system, the result is a single nameserver at 
# 1: 172.16.16.16

# ---------------------------------------------------------
# We could add additional nameservers, such as Google and Cloudfare
$supportsTls = 1;
# Cloudfare
$dns->AddNameserver("1.1.1.1",$supportsTls);
# Google
$dns->AddNameserver("8.8.8.8",$supportsTls);

# See the nameservers now used by Chilkat
$nsCount = $dns->get_NumNameservers();
$i = 0;
while ($i < $nsCount) {
    print ($i + 1) . ": " . $dns->getNameserver($i) . "\r\n";
    $i = $i + 1;
}

# Result:
# 1: 172.16.16.16
# 2: 1.1.1.1
# 3: 8.8.8.8

# ---------------------------------------------------------
# To revert back to the system default nameservers, clear all
# then re-add the default.
$dns->RemoveAllNameservers();
$dns->AddDefaultNameservers();

# See the nameservers now used by Chilkat
$nsCount = $dns->get_NumNameservers();
$i = 0;
while ($i < $nsCount) {
    print ($i + 1) . ": " . $dns->getNameserver($i) . "\r\n";
    $i = $i + 1;
}

# Result:
# 1: 172.16.16.16