Java

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.

Chilkat2 Java

import com.chilkatsoft.chilkat2.Dns;

public class ChilkatExample {

    public static void main(String[] args) {
        // 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 dns = new Dns();

        // 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
        int nsCount = dns.getNumNameservers();
        int i = 0;
        while (i < nsCount) {
            System.out.println((i + 1) + ": " + dns.getNameserver(i));
            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
        boolean supportsTls = true;
        // 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.getNumNameservers();
        i = 0;
        while (i < nsCount) {
            System.out.println((i + 1) + ": " + dns.getNameserver(i));
            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.getNumNameservers();
        i = 0;
        while (i < nsCount) {
            System.out.println((i + 1) + ": " + dns.getNameserver(i));
            i = i + 1;
        }

        // Result:
        // 1: 172.16.16.16
    }
}