/// <summary>
/// Look up a DNS TXT record.
/// </summary>
/// <param name="prefix">The prefix, ending in '.'. Example: "_xmppconnect."</param>
/// <param name="domain">The domain to search</param>
/// <param name="attribute">The attribute name to look for. Example: "_xmpp-client-xbosh"</param>
/// <returns></returns>
public static string LookupTXT(string prefix, string domain, string attribute)
{
if (prefix == null)
throw new ArgumentNullException("prefix");
if (domain == null)
throw new ArgumentNullException("domain");
if (attribute == null)
throw new ArgumentNullException("attribute");
if (!prefix.EndsWith("."))
throw new ArgumentOutOfRangeException("Prefix must end in '.'", "prefix");
try
{
if (Environment.OSVersion.Platform != PlatformID.Unix)
{
DnsRequest request = new DnsRequest(prefix + domain);
DnsResponse response = request.GetResponse(DnsRecordType.TEXT);
string attr = attribute + "=";
foreach (TXTRecord txt in response.TXTRecords)
{
if (txt.StringArray.StartsWith(attr))
{
Debug.WriteLine(string.Format("TXT found: {0}", txt.StringArray));
return txt.StringArray.Substring(attr.Length);
}
}
}
else
{
// FIXME: Add TXT support to UnixDnsResolver...
throw new NotImplementedException();
}
}
catch
{
}
return null;
}
/// <summary>
/// Look up a DNS SRV record, returning the best host and port number to connect to.
/// </summary>
/// <param name="prefix">The SRV prefix, ending with a dot. Example: "_xmpp-client._tcp."</param>
/// <param name="domain">The domain to check</param>
/// <param name="host">The host name to connect to</param>
/// <param name="port">The port number to connect to</param>
public static void LookupSRV(string prefix, string domain, ref string host, ref int port)
{
if (prefix == null)
throw new ArgumentNullException("prefix");
if (domain == null)
throw new ArgumentNullException("domain");
if (!prefix.EndsWith("."))
throw new ArgumentOutOfRangeException("Prefix must end in '.'", "prefix");
try
{
SRVRecord record;
if (Environment.OSVersion.Platform != PlatformID.Unix)
{
DnsRequest request = new DnsRequest(prefix + domain);
DnsResponse response = request.GetResponse(DnsRecordType.SRV);
record = PickSRV(response.SRVRecords);
}
else
{
var records = UnixDnsResolver.ResolveSRV(prefix + domain);
record = PickSRV(records);
}
host = record.NameNext;
port = record.Port;
Debug.WriteLine(string.Format("SRV found: {0}:{1}", host, port));
}
catch
{
host = domain;
}
}
