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(Unicode C) Revert to Default DNS NameserversSee more DNS ExamplesDemonstrates 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.
#include <C_CkDnsW.h> void ChilkatSample(void) { HCkDnsW dns; int nsCount; int i; BOOL supportsTls; // 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 = CkDnsW_Create(); // 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. CkDnsW_AddDefaultNameservers(dns); // Let's examine our nameservers nsCount = CkDnsW_getNumNameservers(dns); i = 0; while (i < nsCount) { wprintf(L"%d: %s\n",i + 1,CkDnsW_getNameserver(dns,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 supportsTls = TRUE; // Cloudfare CkDnsW_AddNameserver(dns,L"1.1.1.1",supportsTls); // Google CkDnsW_AddNameserver(dns,L"8.8.8.8",supportsTls); // See the nameservers now used by Chilkat nsCount = CkDnsW_getNumNameservers(dns); i = 0; while (i < nsCount) { wprintf(L"%d: %s\n",i + 1,CkDnsW_getNameserver(dns,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. CkDnsW_RemoveAllNameservers(dns); CkDnsW_AddDefaultNameservers(dns); // See the nameservers now used by Chilkat nsCount = CkDnsW_getNumNameservers(dns); i = 0; while (i < nsCount) { wprintf(L"%d: %s\n",i + 1,CkDnsW_getNameserver(dns,i)); i = i + 1; } // Result: // 1: 172.16.16.16 CkDnsW_Dispose(dns); } |
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