GetHostEntry is very slow

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Maybe this can help? The WayBack Machine version of the dead link.

(Dead link: http://www.chapleau.info/blog/2008/09/09/reverse-dns-lookup-with-timeout-in-c.html)

The code, for posterity:

private delegate IPHostEntry GetHostEntryHandler(string ip);

public string GetReverseDNS(string ip, int timeout)
{
    try
    {
        GetHostEntryHandler callback = new GetHostEntryHandler(Dns.GetHostEntry);
        IAsyncResult result = callback.BeginInvoke(ip,null,null);
        if (result.AsyncWaitHandle.WaitOne(timeout, false))
        {
            return callback.EndInvoke(result).HostName;
        }
        else
        {
            return ip;
        }
    }
    catch (Exception)
    {
        return ip;
    }
}

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