private static async Task <IPHostEntry> GetHostEntryFromNameAsync(IDnsQuery query, string hostName)
{
if (string.IsNullOrWhiteSpace(hostName))
{
throw new ArgumentNullException(nameof(hostName));
}
var hostString = DnsString.FromResponseQueryString(hostName);
var ipv4Result = query.QueryAsync(hostString, QueryType.A);
var ipv6Result = query.QueryAsync(hostString, QueryType.AAAA);
await Task.WhenAll(ipv4Result, ipv6Result).ConfigureAwait(false);
var allRecords = ipv4Result.Result
.Answers.Concat(ipv6Result.Result.Answers)
.ToArray();
return(GetHostEntryProcessResult(hostString, allRecords));
}
public static async Task <ServiceHostEntry[]> ResolveServiceAsync(this IDnsQuery query, string baseDomain, string serviceName, string tag = null)
{
if (baseDomain == null)
{
throw new ArgumentNullException(nameof(baseDomain));
}
if (string.IsNullOrWhiteSpace(serviceName))
{
throw new ArgumentNullException(nameof(serviceName));
}
string queryString;
if (string.IsNullOrWhiteSpace(tag))
{
queryString = $"{serviceName}.{baseDomain}.";
}
else
{
queryString = $"_{serviceName}._{tag}.{baseDomain}.";
}
var hosts = new List <ServiceHostEntry>();
var result = await query.QueryAsync(queryString, QueryType.SRV);
if (result.HasError)
{
return(hosts.ToArray());
}
foreach (var entry in result.Answers.SrvRecords())
{
var addresses = result.Additionals
.OfType <AddressRecord>()
.Where(p => p.DomainName.Equals(entry.Target))
.Select(p => p.Address);
hosts.Add(new ServiceHostEntry()
{
AddressList = addresses.ToArray(),
HostName = entry.Target.Value,
Port = entry.Port
});
}
return(hosts.ToArray());
}
/// <summary>
/// The <c>ResolveServiceAsync</c> method does a <see cref="QueryType.SRV"/> lookup for <c>_{<paramref name="serviceName"/>}[._{<paramref name="tag"/>}].{<paramref name="baseDomain"/>}</c>
/// and aggregates the result (hostname, port and list of <see cref="IPAddress"/>s) to a <see cref="ServiceHostEntry"/>.
/// <para>
/// This method expects matching A or AAAA records to populate the <see cref="IPHostEntry.AddressList"/>,
/// and/or a <see cref="ResourceRecordType.CNAME"/> record to populate the <see cref="IPHostEntry.HostName"/> property of the result.
/// </para>
/// </summary>
/// <remarks>
/// The returned list of <see cref="IPAddress"/>s and/or the hostname can be empty if no matching additional records are found.
/// </remarks>
/// <param name="query">The <see cref="IDnsQuery"/> instance.</param>
/// <param name="baseDomain">The base domain, which will be appended to the end of the query string.</param>
/// <param name="serviceName">The name of the service to look for. Must not have any <c>_</c> prefix.</param>
/// <param name="tag">An optional tag. Must not have any <c>_</c> prefix.</param>
/// <returns>A collection of <see cref="ServiceHostEntry"/>s.</returns>
/// <exception cref="ArgumentNullException">If <paramref name="baseDomain"/> or <paramref name="serviceName"/> are null.</exception>
/// <seealso href="https://tools.ietf.org/html/rfc2782">RFC 2782</seealso>
public static async Task <ServiceHostEntry[]> ResolveServiceAsync(this IDnsQuery query, string baseDomain, string serviceName, string tag = null)
{
if (query == null)
{
throw new ArgumentNullException(nameof(query));
}
if (baseDomain == null)
{
throw new ArgumentNullException(nameof(baseDomain));
}
if (string.IsNullOrWhiteSpace(serviceName))
{
throw new ArgumentNullException(nameof(serviceName));
}
var queryString = ConcatResolveServiceName(baseDomain, serviceName, tag);
var result = await query.QueryAsync(queryString, QueryType.SRV).ConfigureAwait(false);
return(ResolveServiceProcessResult(result));
}
