C Simple Implementation of SNMP
- 2021-07-18 08:47:46
- OfStack
In this paper, an example is given to describe the simple implementation of SNMP by C #. Share it for your reference. The details are as follows:
/**
C# Network Programming
by Richard Blum
Publisher: Sybex
ISBN: 0782141765
*/
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
public class SimpleSNMP
{
public static void Main(string[] argv)
{
int commlength, miblength, datatype, datalength, datastart;
int uptime = 0;
string output;
SNMP conn = new SNMP();
byte[] response = new byte[1024];
Console.WriteLine("Device SNMP information:");
// Send sysName SNMP request
response = conn.get("get", argv[0], argv[1], "1.3.6.1.2.1.1.5.0");
if (response[0] == 0xff)
{
Console.WriteLine("No response from {0}", argv[0]);
return;
}
// If response, get the community name and MIB lengths
commlength = Convert.ToInt16(response[6]);
miblength = Convert.ToInt16(response[23 + commlength]);
// Extract the MIB data from the SNMP response
datatype = Convert.ToInt16(response[24 + commlength + miblength]);
datalength = Convert.ToInt16(response[25 + commlength + miblength]);
datastart = 26 + commlength + miblength;
output = Encoding.ASCII.GetString(response, datastart, datalength);
Console.WriteLine(" sysName - Datatype: {0}, Value: {1}",
datatype, output);
// Send a sysLocation SNMP request
response = conn.get("get", argv[0], argv[1], "1.3.6.1.2.1.1.6.0");
if (response[0] == 0xff)
{
Console.WriteLine("No response from {0}", argv[0]);
return;
}
// If response, get the community name and MIB lengths
commlength = Convert.ToInt16(response[6]);
miblength = Convert.ToInt16(response[23 + commlength]);
// Extract the MIB data from the SNMP response
datatype = Convert.ToInt16(response[24 + commlength + miblength]);
datalength = Convert.ToInt16(response[25 + commlength + miblength]);
datastart = 26 + commlength + miblength;
output = Encoding.ASCII.GetString(response, datastart, datalength);
Console.WriteLine(" sysLocation - Datatype: {0}, Value: {1}", datatype, output);
// Send a sysContact SNMP request
response = conn.get("get", argv[0], argv[1], "1.3.6.1.2.1.1.4.0");
if (response[0] == 0xff)
{
Console.WriteLine("No response from {0}", argv[0]);
return;
}
// Get the community and MIB lengths
commlength = Convert.ToInt16(response[6]);
miblength = Convert.ToInt16(response[23 + commlength]);
// Extract the MIB data from the SNMP response
datatype = Convert.ToInt16(response[24 + commlength + miblength]);
datalength = Convert.ToInt16(response[25 + commlength + miblength]);
datastart = 26 + commlength + miblength;
output = Encoding.ASCII.GetString(response, datastart, datalength);
Console.WriteLine(" sysContact - Datatype: {0}, Value: {1}",
datatype, output);
// Send a SysUptime SNMP request
response = conn.get("get", argv[0], argv[1], "1.3.6.1.2.1.1.3.0");
if (response[0] == 0xff)
{
Console.WriteLine("No response from {0}", argv[0]);
return;
}
// Get the community and MIB lengths of the response
commlength = Convert.ToInt16(response[6]);
miblength = Convert.ToInt16(response[23 + commlength]);
// Extract the MIB data from the SNMp response
datatype = Convert.ToInt16(response[24 + commlength + miblength]);
datalength = Convert.ToInt16(response[25 + commlength + miblength]);
datastart = 26 + commlength + miblength;
// The sysUptime value may by a multi-byte integer
// Each byte read must be shifted to the higher byte order
while(datalength > 0)
{
uptime = (uptime << 8) + response[datastart++];
datalength--;
}
Console.WriteLine(" sysUptime - Datatype: {0}, Value: {1}",
datatype, uptime);
}
}
class SNMP
{
public 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, i;
int orgmiblen = miblen;
int pos = 0;
// Convert the string MIB into a byte array of integer values
// Unfortunately, values over 128 require multiple bytes
// which also increases the MIB length
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; //Length of entire SNMP packet
//The SNMP sequence start
packet[pos++] = 0x30; //Sequence start
packet[pos++] = Convert.ToByte(snmplen - 2); //sequence size
//SNMP version
packet[pos++] = 0x02; //Integer type
packet[pos++] = 0x01; //length
packet[pos++] = 0x00; //SNMP version 1
//Community name
packet[pos++] = 0x04; // String type
packet[pos++] = Convert.ToByte(comlen); //length
//Convert community name to byte array
byte[] data = Encoding.ASCII.GetBytes(community);
for (i = 0; i < data.Length; i++)
{
packet[pos++] = data[i];
}
//Add GetRequest or GetNextRequest value
if (request == "get")
packet[pos++] = 0xA0;
else
packet[pos++] = 0xA1;
packet[pos++] = Convert.ToByte(20 + miblen - 1); //Size of total MIB
//Request ID
packet[pos++] = 0x02; //Integer type
packet[pos++] = 0x04; //length
packet[pos++] = 0x00; //SNMP request ID
packet[pos++] = 0x00;
packet[pos++] = 0x00;
packet[pos++] = 0x01;
//Error status
packet[pos++] = 0x02; //Integer type
packet[pos++] = 0x01; //length
packet[pos++] = 0x00; //SNMP error status
//Error index
packet[pos++] = 0x02; //Integer type
packet[pos++] = 0x01; //length
packet[pos++] = 0x00; //SNMP error index
//Start of variable bindings
packet[pos++] = 0x30; //Start of variable bindings sequence
packet[pos++] = Convert.ToByte(6 + miblen - 1); // Size of variable binding
packet[pos++] = 0x30; //Start of first variable bindings sequence
packet[pos++] = Convert.ToByte(6 + miblen - 1 - 2); // size
packet[pos++] = 0x06; //Object type
packet[pos++] = Convert.ToByte(miblen - 1); //length
//Start of MIB
packet[pos++] = 0x2b;
//Place MIB array in packet
for(i = 2; i < miblen; i++)
packet[pos++] = Convert.ToByte(mib[i]);
packet[pos++] = 0x05; //Null object value
packet[pos++] = 0x00; //Null
//Send packet to destination
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);
//Receive response from packet
try
{
int recv = sock.ReceiveFrom(packet, ref ep);
} catch (SocketException)
{
packet[0] = 0xff;
}
return packet;
}
public string getnextMIB(byte[] mibin)
{
string output = "1.3";
int commlength = mibin[6];
int mibstart = 6 + commlength + 17; //find the start of the mib section
//The MIB length is the length defined in the SNMP packet
// minus 1 to remove the ending .0, which is not used
int miblength = mibin[mibstart] - 1;
mibstart += 2; //skip over the length and 0x2b values
int mibvalue;
for(int i = mibstart; i < mibstart + miblength; i++)
{
mibvalue = Convert.ToInt16(mibin[i]);
if (mibvalue > 128)
{
mibvalue = (mibvalue/128)*128 + Convert.ToInt16(mibin[i+1]);
//ERROR here, it should be mibvalue = (mibvalue-128)*128 + Convert.ToInt16(mibin[i+1]);
//for mib values greater than 128, the math is not adding up correctly
i++;
}
output += "." + mibvalue;
}
return output;
}
}
I hope this article is helpful to everyone's C # programming.