SADPTool原理：

向239.255.255.250：37020发送基于ONVIF协议的 udp 组播,设备会监听 239.255.255.250：37020，收到指令，会向 发送组播的机器，返回设备信息，也会向239.255.255.250：37020 发送 设备信息的 组播。

发送 报文（Uuid是Guid，每次都生成一个新的）

<?xml version="1.0" encoding="utf-8"?><Probe><Uuid>12D17626-0DE1-48DB-97E3-40B106467932</Uuid><Types>inquiry</Types></Probe>

返回报文

<?xml version="1.0" encoding="UTF-8" ?>
<ProbeMatch>
<Uuid>12D17626-0DE1-48DB-97E3-40B106467932</Uuid>
<Types>inquiry</Types>
<DeviceType>139991</DeviceType>
<DeviceDescription>CS-C6TC-32WFR</DeviceDescription>
<DeviceSN>CS-C6TC-32WFR0120170327CCCH738231995</DeviceSN>
<CommandPort>8000</CommandPort>
<HttpPort>80</HttpPort>
<MAC>54-c4-15-9a-38-72</MAC>
<IPv4Address>172.20.20.100</IPv4Address>
<IPv4SubnetMask>255.255.255.0</IPv4SubnetMask>
<IPv4Gateway>172.20.20.254</IPv4Gateway>
<DHCP>false</DHCP>
<AnalogChannelNum>0</AnalogChannelNum>
<DigitalChannelNum>1</DigitalChannelNum>
<SoftwareVersion>V5.2.3build 180804</SoftwareVersion>
<DSPVersion>V1.0 build 180731</DSPVersion>
<BootTime>2018-10-18 21:30:10</BootTime>
<OEMInfo>N/A</OEMInfo>
<Activated>true</Activated>
<PasswordResetAbility>false</PasswordResetAbility>
</ProbeMatch>

实现代码：

using System.Net.Sockets;
using System.Net;
using System.Text;
using System;
using System.Threading.Tasks;

namespace ConsoleApp
{
    class Program
    {

        public static void Main(string[] args)
        {
            var localIp = "192.168.51.215";//本地ip
            UdpClient client = new UdpClient(new IPEndPoint(IPAddress.Parse(localIp), 37020));
            Task.Factory.StartNew(() =>
            {
                
                IPEndPoint mult = null;
                while (true)
                {
                    byte[] buf = client.Receive(ref mult);
                    string msg = Encoding.ASCII.GetString(buf);
                    Console.WriteLine(msg);
                }
            });

            var xml = $"<?xml version=\"1.0\" encoding=\"utf-8\"?><Probe><Uuid>{Guid.NewGuid().ToString().ToUpper()}</Uuid><Types>inquiry</Types></Probe>";
            var bytes = Encoding.ASCII.GetBytes(xml);
            IPEndPoint multicast = new IPEndPoint(IPAddress.Parse("239.255.255.250"), 37020);
            client.Send(bytes, bytes.Length, multicast);
            
            Console.ReadKey();
        }

    }
}