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Who Should Read This

  1. You want to program SNMP with C# but have no idea for beginning.
  2. You've googled for a while, but don't get a simple working example.
  3. What you're looking for, is just a simple requirement to get a status value from a device through SNMP.

Introduction
My purpose is to get an uint value from a temperature sensor through SNMP. This is a very simple requirement, and I don't want to understand the whole detail of SNMP protocol. In JAVA, there's lot of open source resources for SNMP programming, for example, SNMP4j. How ever, I found no simple guidance for C# SNMP programming. If you have the same problem, you can have following example to start your way toward SNMP.

Pre-requirement
  1. C# Programming Basics
  2. A working SNMP host to communicate with. For example, a temperature sensor, a networked printer or a router with SNMP functions.
Sample SNMP Class
Firstly, you have to add a reference to OLEPRNLIB. You can find it from "Add reference" -> "COM". The path of the dll is located at C:\Windows\System32 by Default.

Here is a sample SNMP Class:

using System;
using System.Collections.Generic;
using System.Text;
using OLEPRNLib;

namespace MrFu
{
public class SimpleSnmp
{
private String hostIp;
private String oid;
private String communityString;

int retries = 1;
int timeout = 3000;

SNMP snmp = new SNMP();

public SimpleSnmp(String hostIp, String communityString, String oid)
{
this.hostIp = hostIp;
this.communityString = communityString;
this.oid = oid;

try
{
snmp.Open(this.hostIp, this.communityString, this.retries, this.timeout);
}
catch (Exception ex) {
Console.WriteLine(ex.Message);
}

}

public String getValue() {
try
{
uint result = snmp.GetAsByte(this.oid);
return result.ToString();
}
catch (Exception ex) {
Console.WriteLine(ex.Message);
return null;
}
}
}
}


Description for the Code

First line you need to look at is:
snmp.Open(this.hostIp, this.communityString, this.retries, this.timeout);
where the "hostIp" is the IP address of the target, of course,

the "communityString" is "public" by default for most SNMP device. If you changed it on device configuration, remember to modify it.

the "retries" and "timeout" indicate how many times the system should retry if connection failed over the milliseconds given by "timeout".

And, That's All to Connect to A Device Through SNMP. COOL!

Second line you might want to know is:
uint result = snmp.GetAsByte(this.oid);
That's the basic way to get the status or value from your host device. You can convert it into String or any thing you like.

To explain in a simple way, the "oid" is the unique id for some status on the device. You can obtain the correct oid from your device manual. For example, the oid of my temperature sensor is:
".1.3.6.1.4.1.3854.1.2.2.1.16.1.3.0"
So you should be able to find some string looks like that from your device suppliers or documents.

For more detailed description of SNMP protocol, you can look into wikipedia.

That's all. So easy, and you can have a first shot of SNMP programming with C# now.


Conclusin
This is quiet a easy way to have a quick look of SNMP progamming with C#. Surely, the detailed packet parsing or other SNMP functions are NOT shown in this post. But that's all I need to solve my problem. And I hope this post can help you, too.
posted on 2009-06-18 15:30 Vincent-chen 阅读(1188) 评论(1)  编辑  收藏 所属分类: snmp

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