条件：

1.拥有一台具有外网地址的服务器，如：54.243.209.209；

2.设置防火墙策略，放行53/UDP端口的通讯；

3.设置域名subA.mooo.com 的 A记录为 54.243.209.209

4.设置域名subB.mooo.com 的 NameServer为 subA.mooo.com

5.根据以上设置，但我们请求解析xxx.subB.mooo.com的域名时，54.243.209.209会收到来自DNS服务器的DNS请求数据包；

6.响应这个数据包就可以完成一次标准的DNS请求响应；

7.构造特殊的域名就可以实现特征数据的传递；

C#编程实现实现DNS请求客户端

新建一个C#项目，使用dotNet Framework 3.5作为运行环境。添加对库文件“ARSoft.Tools.Net.dll”的引用。编写如下代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ARSoft.Tools.Net.Dns;
 
namespace MyDNSClient
{
    /// <summary>
    /// @auth shadu{AT}foxmail.com
    /// @desc C# DNS Client
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
            //ClientQuery("www.baidu.com");
            ClientQuery("xxx.subB.mooo.com");
            Console.ReadKey();
        }
 
        public static void ClientQuery(string domain)
        {
            DnsMessage dnsMessage = DnsClient.Default.Resolve(domain, RecordType.A);
            if ((dnsMessage == null) || ((dnsMessage.ReturnCode != ReturnCode.NoError) && (dnsMessage.ReturnCode != ReturnCode.NxDomain)))
            {
                Console.WriteLine("DNS request failed");
            }
            else
            {
                foreach (DnsRecordBase dnsRecord in dnsMessage.AnswerRecords)
                {
                    ARecord aRecord = dnsRecord as ARecord;
                    if (aRecord != null)
                    {
                        Console.WriteLine("DNS request successfully : {0}",aRecord.Address.ToString());
                    }
                }
            }
        }
    }
}

C#编程实现实现DNS响应服务端

新建一个C#项目，使用dotNet Framework 3.5作为运行环境。添加对库文件“ARSoft.Tools.Net.dll”的引用。编写如下代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ARSoft.Tools.Net.Dns;
using System.Net;
 
 
namespace DNSServer
{
    /// <summary>
    /// @auth shadu{AT}foxmail.com
    /// @desc C# DNS Server
    /// </summary>
    class Program
    {
        static void Main(string[] args)
        {
            using (DnsServer server = new DnsServer(IPAddress.Any, 10, 10, ProcessQuery))
            {
                server.Start();
                Console.WriteLine("Press any key to stop server");
                Console.ReadLine();
            }
        }
 
        static DnsMessageBase ProcessQuery(DnsMessageBase message, IPAddress clientAddress, System.Net.Sockets.ProtocolType protocol)
        {
            message.IsQuery = false;
            DnsMessage query = message as DnsMessage;
 
            // 官方的样例文档中没有体现DNS请求发起者的IP，我在这里增加了。
            Console.WriteLine("Client Address:{0}", clientAddress.ToString()); 
            Console.WriteLine("query.Questions.Count:{0}", query.Questions.Count);
            Console.WriteLine("query.Questions.ToString():{0}", query.Questions.ToString());
            Console.WriteLine("query.Questions[0].ToString():{0}", query.Questions[0].ToString());
            Console.WriteLine("query.Questions[0].GetType():{0}", query.Questions[0].GetType().ToString()); 
            Console.WriteLine("query.Questions[0].Name:{0}", query.Questions[0].Name.ToString());
            Console.WriteLine("query.Questions[0].RecordType:{0}", query.Questions[0].RecordType.ToString());
            Console.WriteLine("query.Questions[0].RecordClass {0}", query.Questions[0].RecordClass.ToString());
 
            if (query.Questions[0].Name.Contains("subB.mooo.com"))
            {
 
                Console.WriteLine("Contains subB.mooo.com");
                query.AnswerRecords.Add(new ARecord("xxx.subB.mooo.com", 3600, IPAddress.Parse("9.9.9.9")));
                message.ReturnCode = ReturnCode.NoError;
                return message;
 
            }
            else
            {
                Console.WriteLine("!!! not Contains mooo");
                message.ReturnCode = ReturnCode.ServerFailure;
                Console.WriteLine(message.ReturnCode.ToString());
 
                return message;
            }
        }
    }
}