B4X

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.

B4X

'  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 ChilkatDns
dns.Initialize("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 Int = dns.NumNameservers
Dim i As Int = 0
Do While i < nsCount
    Log((i + 1) & ": " & dns.GetNameserver(i))
    i = i + 1
Loop

'  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
Do While i < nsCount
    Log((i + 1) & ": " & dns.GetNameserver(i))
    i = i + 1
Loop

'  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
Do While i < nsCount
    Log((i + 1) & ": " & dns.GetNameserver(i))
    i = i + 1
Loop

'  Result:
'  1: 172.16.16.16