snmp-blog

Author: zd987

This is an SNMP Agent demo code forked from https://github.com/jrask/snmp-blog

Mainly derived from open source project SNMP4J-AGENT

Quick start of SNMP protocol

It is a little difficult for a beginer to develop software with SNMP protocol. It took me quite a lot time to learn what is SNMP, the glossary and how it works. Here are some useful links that can help you learn it easily:

Introduction to snmp4j: An useful artical teaching you how to write SNMP manager / agent.

snmp_tutorial.pdf: A very good white-paper that tells you the detailed information about SNMP from the administrator perspective. Here is the offical link.

SNMP中文介绍.pdf: An introduction about SNMP protocol in Chinese.

After you get a quick view about SNMP, you can dive into the code and modify its function for your intention.

Environment Setup

You can setup the snmp agent / manager by using several existing tools. In my case, I use linux snmp service as the aggent(in vmware as virtual machine), and use AdventNet SNMP Utilities (its new version is called WebNMS SNMP Utilities 5) in windows as manager. In manager part, I use MIBBrowser to GET the OID value by SNMP, and use Trap Viewer to monitor the TRAP message.

If you wonder how SNMP protocol works, you can check its protocol message content. Here I use Wireshark as the network protocol analyzer. Notice that wireshark could not track the message of localhost(127.0.0.1) on windows platform. You can refer to the workaround.

Design MIB

In order to make our own SNMP application, we need to define the MIB. Here I use two commercial tools to help do the work: MIBDesigner for visually design the MIB structure information, and AgenPro for automatically generate Java code from MIB txt from the first step.

Code Introduction

The main class is com.jayway.snmpblogg.Agent. It ripped out the SNMPv3 code from BaseAgent and makes it more easy for learning. My use case is to extract the key field value from the predefined servlet status page and exposed as SNMP agent. My code update the original version for several parts:

Add trap(SNMP v1) / notification(SNMP v2c) message test.
Add MIB information update mechnism.

Command Run

If you want to build a java application that run on the command line, you can refer to the dist\run.bat file. Here you need to add all the required jars in the classpath, and specify the main class.