(SQL Server) 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 ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- 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.

    DECLARE @dns int
    -- Use "Chilkat_9_5_0.Dns" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Dns', @dns OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    -- 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.
    EXEC sp_OAMethod @dns, 'AddDefaultNameservers', NULL

    -- Let's examine our nameservers
    DECLARE @nsCount int
    EXEC sp_OAGetProperty @dns, 'NumNameservers', @nsCount OUT
    DECLARE @i int
    SELECT @i = 0
    WHILE @i < @nsCount
      BEGIN

        EXEC sp_OAMethod @dns, 'GetNameserver', @sTmp0 OUT, @i
        PRINT @i + 1 + ': ' + @sTmp0
        SELECT @i = @i + 1
      END

    -- 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
    DECLARE @supportsTls int
    SELECT @supportsTls = 1
    -- Cloudfare
    EXEC sp_OAMethod @dns, 'AddNameserver', NULL, '1.1.1.1', @supportsTls
    -- Google
    EXEC sp_OAMethod @dns, 'AddNameserver', NULL, '8.8.8.8', @supportsTls

    -- See the nameservers now used by Chilkat
    EXEC sp_OAGetProperty @dns, 'NumNameservers', @nsCount OUT
    SELECT @i = 0
    WHILE @i < @nsCount
      BEGIN

        EXEC sp_OAMethod @dns, 'GetNameserver', @sTmp0 OUT, @i
        PRINT @i + 1 + ': ' + @sTmp0
        SELECT @i = @i + 1
      END

    -- 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.
    EXEC sp_OAMethod @dns, 'RemoveAllNameservers', NULL
    EXEC sp_OAMethod @dns, 'AddDefaultNameservers', NULL

    -- See the nameservers now used by Chilkat
    EXEC sp_OAGetProperty @dns, 'NumNameservers', @nsCount OUT
    SELECT @i = 0
    WHILE @i < @nsCount
      BEGIN

        EXEC sp_OAMethod @dns, 'GetNameserver', @sTmp0 OUT, @i
        PRINT @i + 1 + ': ' + @sTmp0
        SELECT @i = @i + 1
      END

    -- Result:
    -- 1: 172.16.16.16

    EXEC @hr = sp_OADestroy @dns


END
GO