DnsClient.NETを利用したDNSへの問い合わせ

DnsLookup.cs

    /// <summary>
    /// DNSへの問い合わせクラス
    /// </summary>
    public class DnsLookup
    {
        /// <summary>
        /// DNSへ問い合わせを行いSRVレコードとAレコードからサービスのホストを取得します。
        /// </summary>
        /// <param name="lookupName">問い合わせを行うSRVレコードに対応したNamespace</param>
        /// <returns><see cref="ServiceHost"/></returns>
        public async Task<ServiceHost> Execute(string lookupName)
        {
            var client = new LookupClient {UseCache = true};

            var result = await client.QueryAsync(lookupName, QueryType.SRV);
            Console.WriteLine($"result.Header={result.Header}");

            if (result.HasError)
            {
                return ServiceHost.Build();
            }

            var srvRecord = result.Answers.OfType<SrvRecord>().FirstOrDefault();
            if (srvRecord == null)
            {
                return ServiceHost.Build();
            }
            
            var aRecordResult = await client.QueryAsync(srvRecord.Target, QueryType.A);
            var aRecord = aRecordResult.Answers.OfType<ARecord>().FirstOrDefault();
            if (aRecord == null)
            {
                return ServiceHost.Build();
            }

            return ServiceHost.Build(aRecord.Address.ToString(), srvRecord.Port);
        }
    }

    public class ServiceHost
    {
        public string IpAddress { get; }
        public int? Port { get; }

        private ServiceHost(string ipAddress, int? port)
        {
            IpAddress = ipAddress;
            Port = port;
        }

        public static ServiceHost Build(string ipAddress, int port)
        {
            return new ServiceHost(ipAddress, port);
        }

        public static ServiceHost Build()
        {
            return new ServiceHost("", null);
        }

        public string BaseUrl()
        {
            if (string.IsNullOrEmpty(IpAddress))
            {
                return "";
            }

            if (!Port.HasValue)
            {
                return "";
            }

            return $"http://{IpAddress}:{Port}/";
        }
    }