CDNS 1.0 - An MFC DNS class

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Introduction

I needed to use DNS lookups in a little Internet app I was using, and couldn't find a manageable solution. So I created one.

What are DNS lookups and why would you use one?

DNS stands for Domain Name Server/Service. It is the method which all browsers use to resolve hostnames (www.codeproject.com, for example) into IP addresses they can connect to.

How does this code work?

In my class, I have used a few Winsock functions to do the lookups, mainly GetHostByName to fill the hostent structure with information. The basic process is:

• WSAStartup to initialize.
• GetHostByName to fill the hostent structure.
• Check if any information was retrieved.
• If so, loop through the returned IPs and hostnames and add them to an array.
• WSACleanup to end the process.

Using the class

The main three functions that will be used are:

• SetHostname
• DoDNSLookup
• GetIPAt

An example of retrieving a hostname's primary IP is:

// Define a CDNS object

CDNS dnsObj;

// Set the hostname

dnsObj.SetHostname("www.google.be");

// Do the DNS lookup

BOOL doLookup = dnsObj.DoDNSLookup;

if (doLookup)
{
    // Retrieve the IP

    CString thisIP = dnsObj.GetIPAt(0);
}

Of course, the class retrieves multiple IPs, so you'll need to do a loop to get them all. Here's an example:

// Define a CDNS object

CDNS dnsObj;

// Set the hostname

dnsObj.SetHostname("www.google.be");

// Do the DNS lookup

BOOL doLookup = dnsObj.DoDNSLookup;

if (doLookup)
{
    for (int i = 0; i <= dnsObj.GetNumberOfIP(); i++)
    {
        CString thisIP = dnsObj.GetIPAt(i);
        // Do something with the IP

    }
}

History

• 1.0
  • 22^nd May, 2005: First public release.