C#利用dig命令解析SRV方法的具体实现

利用dig命令查询SRV服务器的方法
1. 什么是SRV
SRV是DNS服务器的数据库中支持的一种资源记录的类型，它记录了哪台计算机提供了哪个服务这么一个简单的信息。在DNS服务器上可以做SRV的配置，使用SRV的好处是需要使用SRV服务的客户端程序不再需要固定SRV服务器的IP地址，这样就增加了灵活性。SRV的详细说明可以参考：http://en.wikipedia.org/wiki/SRV_record

2. 如何解析SRV服务
查询和解析SRV服务可以使用dig命令和nslookup，其中dig既支持windows平台又支持linux平台，是比较好的选择。在各类应用程序中可以通过采用执行系统命令（dig.exe或dig）的方式来解析SRV记录。

3. C# 例子

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Diagnostics;

namespace SRVTest
{
    class Program
    {
        static void Main(string[] args)
        {
            string digCmd = "dig.exe";
            string srv = "@192.168.0.10 srv _test._tcp.testsrv.com +short";
            ArrayList serverList = new ArrayList();

            ArrayList outputList = executeCmd(digCmd, srv);                    //第一次获取SRV服务名称字符串
            for (int i = 0; i < outputList.Count; i++)
            {
                string output = (string)outputList[i];
                if (output.Contains("timed out"))
                    continue;
                System.Console.WriteLine("Test srv:" + output);
                string[] parts = output.Split(' ');
                if (parts.Length < 4)
                    continue;
                string srvName = parts[3];
                string srv2 = "@192.168.0.10 " + srvName.Substring(0, srvName.Length - 1) + " " + " +short";
                ArrayList outputList2 = executeCmd(digCmd, srv2);              //第二次根据SRV服务名称获取对应的IP地址字符串
                serverList.AddRange(outputList2);
            }

            for (int i = 0; i < serverList.Count; i++)
            {
                string server = (string)serverList[i];
                System.Console.WriteLine("server " + i + ": " + server);         //真正提供testsrv服务的服务器地址
            }

        }
    
    //执行系统命令获取输出结果
        public static ArrayList executeCmd(String cmdName, String args)
        {
            ArrayList outputList = new ArrayList();
            try
            {
                ProcessStartInfo psi = new ProcessStartInfo();
                psi.RedirectStandardError = true;
                psi.RedirectStandardInput = true;
                psi.RedirectStandardOutput = true;
                psi.UseShellExecute = false;
                psi.CreateNoWindow = true;
                psi.WindowStyle = ProcessWindowStyle.Maximized;
                psi.FileName = cmdName;
                psi.Arguments = args;

                System.Console.WriteLine("execute command \"" + psi.FileName + " " + psi.Arguments + "\"");

                Process prc = Process.Start(psi);
                string output = "", errorOutput = "";

                while ((output = prc.StandardOutput.ReadLine()) != null)
                {
                    System.Console.WriteLine("Output:" + output);
                    outputList.Add(output);
                }
                while ((errorOutput = prc.StandardError.ReadLine()) != null)
                {
                    System.Console.WriteLine("Error output:" + errorOutput);
                }
                prc.WaitForExit(10000);
            }
            catch (Exception e)
            {
                System.Console.WriteLine(e.Message);
            }
            return outputList;
        }

    }
}

执行结果：

C:\xxx\dig>SRVTest.exe
execute command "dig.exe @192.168.0.10 srv _test._tcp.testsrv.com +short"
Output:0 0 24633 test200.testsrv.com.
Output:0 0 24633 test201.testsrv.com.
Test srv:0 0 24633 test200.testsrv.com.
execute command "dig.exe @192.168.0.10 test200.testsrv.com  +short"
Output:192.168.0.200
Test srv:0 0 24633 test201.testsrv.com.
execute command "dig.exe @192.168.0.2 test201.testsrv.com  +short"
Output:192.168.0.201
server 0: 192.168.0.200
server 1: 192.168.0.201