.NET环境下的SNMP编程

下面的例子是通过SNMP获取指定IP的机器名。

using System;
using System.Text;
using System.Net;
using System.Net.Sockets;

namespace ConsoleSNMP
{
    public class Program
    {
        static void Main()
        {
            string host = "192.168.1.1";
            string communityName = "public";

            SNMP conn = new SNMP();
            byte[] response = new byte[1024];

            Console.WriteLine("Device SNMP information:");

            response = conn.get("GetRequest", host, communityName, "1.3.6.1.2.1.1.5.0");
            if (response[0] == 0xff)
            {
                Console.WriteLine("No response from {0}", host);
                return;
            }

            int commlength = Convert.ToInt16(response[6]);
            int miblength = Convert.ToInt16(response[23 + commlength]);

            int datatype = Convert.ToInt16(response[24 + commlength + miblength]);
            int datalength = Convert.ToInt16(response[25 + commlength + miblength]);
            int datastart = 26 + commlength + miblength;
            string output = Encoding.ASCII.GetString(response, datastart, datalength);
            Console.WriteLine("  机器名: - Datatype: {0}, Value: {1}",
                    datatype, output);

            Console.ReadLine();
        }
    }
    class SNMP
    {
        public byte[] get(string request, string host, string community, string mibstring)
        {
            byte[] packet = new byte[1024];
            byte[] mib = new byte[1024];
            int snmplen;
            int comlen = community.Length;
            string[] mibvals = mibstring.Split('.');
            int miblen = mibvals.Length;
            int cnt = 0, temp=0, i=0;
            int orgmiblen = miblen;
            int pos = 0;

            //将mib字符串格式转换为整数格式，如果值大于128需要多个字节空间保存，同时增加mib库的长度
            for (i = 0; i < orgmiblen; i++)
            {
                temp = Convert.ToInt16(mibvals[i]);
                if (temp > 127)
                {
                    mib[cnt] = Convert.ToByte(128 + (temp / 128));
                    mib[cnt + 1] = Convert.ToByte(temp - ((temp / 128) * 128));
                    cnt += 2;
                    miblen++;
                }
                else
                {
                    mib[cnt] = Convert.ToByte(temp);
                    cnt++;
                }
            }

            snmplen = 29 + comlen + miblen - 1;

            //snmp包序列开始
            packet[pos++] = 0x30;
            packet[pos++] = Convert.ToByte(snmplen - 2);

            //snmp版本号
            packet[pos++] = 0x02;//整数类型
            packet[pos++] = 0x01;//长度
            packet[pos++] = 0x01;//snmp 版本1

            //团体名称
            packet[pos++] = 0x04;//字符串类型
            packet[pos++] = Convert.ToByte(comlen);//团体名称长度
            byte[] data = Encoding.ASCII.GetBytes(community);
            for (i = 0; i < data.Length; i++)
            {
                packet[pos++] = data[i];//转化团体名称到包中
            }

            //添加GetRequest 或是GetNextRequest 值
            if (request == "GetRequest")
            {
                packet[pos++] = 0xA0;
            }
            else
            {
                packet[pos++] = 0xA1;
            }

            packet[pos++] = Convert.ToByte(20 + miblen - 1);

            //Request ID
            packet[pos++] = 0x02;//整数类型
            packet[pos++] = 0x04;//长度
            packet[pos++] = 0x00;//SNMP request ID
            packet[pos++] = 0x00;
            packet[pos++] = 0x00;
            packet[pos++] = 0x01;

            //错误状态
            packet[pos++] = 0x02;//整数类型
            packet[pos++] = 0x01;//长度
            packet[pos++] = 0x00;//SNMP错误类型

            //错误索引
            packet[pos++] = 0x02;//整数类型
            packet[pos++] = 0x01;//长度
            packet[pos++] = 0x00;//SNMP错误索引

            packet[pos++] = 0x30;//不同对象序列开始标志
            packet[pos++] = Convert.ToByte(6 + miblen - 1);//不同对象的长度
            packet[pos++] = 0x30;//对象序列的开始
            packet[pos++] = Convert.ToByte(6 + miblen - 1 - 2);//尺寸
            packet[pos++] = 0x06;//对象类型
            packet[pos++] = Convert.ToByte(miblen - 1);//长度

            //MIB信息开始位置
            packet[pos++] = 0x2b;
            //把MIB数字放入包中
            for (i = 2; i < miblen; i++)
            {
                packet[pos++] = Convert.ToByte(mib[i]);
            }
            packet[pos++] = 0x05;//空对象值
            packet[pos++] = 0x00;//空

            //通过Socket把包送到指定机器
            Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
            sock.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 5000);
            IPHostEntry ihe = Dns.Resolve(host);
            IPEndPoint iep = new IPEndPoint(ihe.AddressList[0], 161);
            EndPoint ep = (EndPoint)iep;
            
            sock.SendTo(packet, snmplen, SocketFlags.None, iep);

            try
            {
                int recv = sock.ReceiveFrom(packet, ref ep);//接受返回数据
            }
            catch (SocketException)
            {
                packet[0] = 0xff;
            }

            return packet;
        }
    }
}

运行结果如下图：