VB.NET

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.

VB.NET

' 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.

Dim dns As New Chilkat.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
Dim nsCount As Integer = dns.NumNameservers
Dim i As Integer = 0
While i < nsCount
    Debug.WriteLine((i + 1) & ": " & dns.GetNameserver(i))
    i = i + 1
End While

' 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
Dim supportsTls As Boolean = 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.NumNameservers
i = 0
While i < nsCount
    Debug.WriteLine((i + 1) & ": " & dns.GetNameserver(i))
    i = i + 1
End While

' 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.NumNameservers
i = 0
While i < nsCount
    Debug.WriteLine((i + 1) & ": " & dns.GetNameserver(i))
    i = i + 1
End While

' Result:
' 1: 172.16.16.16