/// <summary>
/// Implements the IComparable interface so that we can sort the SRV records by their
/// lowest priority
/// </summary>
/// <param name="other">the other SRVRecord to compare against</param>
/// <returns>1, 0, -1</returns>
public int CompareTo(object obj)
{
SRVRecord srvOther = (SRVRecord)obj;
// we want to be able to sort them by priority from lowest to highest.
if (m_Priority < srvOther.m_Priority)
{
return(-1);
}
if (m_Priority > srvOther.m_Priority)
{
return(1);
}
// if the priority is the same, sort by highest weight to lowest (higher
// weighting means that server should get more of the requests)
if (m_Weight > srvOther.m_Weight)
{
return(-1);
}
if (m_Weight < srvOther.m_Weight)
{
return(1);
}
return(0);
}
/// <summary>
/// Shorthand form to make SRV querying easier, essentially wraps up the retreival
/// of the SRV records, and sorts them by preference
/// </summary>
/// <param name="domain">domain name to retreive SRV RRs for</param>
/// <param name="dnsServer">the server we're going to ask</param>
/// <returns>An array of SRVRecords</returns>
public static SRVRecord[] SRVLookup(string domain, IPAddress dnsServer)
{
// check the inputs
if (domain == null)
{
throw new ArgumentNullException("domain");
}
if (dnsServer == null)
{
throw new ArgumentNullException("dnsServer");
}
// create a request for this
Request request = new Request();
// add one question - the SRV IN lookup for the supplied domain
request.AddQuestion(new Question(domain, DnsType.SRV, DnsClass.IN));
// fire it off
Response response = Lookup(request, dnsServer);
// if we didn't get a response, then return null
if (response == null)
{
return(null);
}
// create a growable array of SRV records
ArrayList resourceRecords = new ArrayList();
// add each of the answers to the array
foreach (Answer answer in response.Answers)
{
// if the answer is an SRV record
if (answer.Type == DnsType.SRV)
{
// add it to our array
resourceRecords.Add(answer.Record);
}
}
// create array of MX records
SRVRecord[] srvRecords = new SRVRecord[resourceRecords.Count];
// copy from the array list
resourceRecords.CopyTo(srvRecords);
// sort into lowest preference order
Array.Sort(srvRecords);
// and return
return(srvRecords);
}
