[SNMP4J] My Hello World app !!!

[Muralidharan Narayanan]

Hello Jaimes:

I used your HelloWorldSNMP.java application on my windows XP machine but I
am getting the following errors. Do you or anybody else who have tried this
know why it is happening.

ONe thing I can see is that the response PDU is null and that is why I am
exceptions are thrown as shown below. Does that mean there is no agent
daemon running on my PC?

Murali

******************** The program *******************
/*
 * HelloWorldSNMP.java
 *
 * @author rodolfojcj
 * @version 1.0
 * This is my first app using SNMP4J package.
 * My goal with it is to send a message with a GET PDU
 * to my computer, which is running a snmp daemon.
 * In this example, only the sysName (1.3.6.2.1.1.5.0) object is requested
 *
 * I've just tested it in this scenario:
 * - O.S. Linux Fedora Core 1
 * - snmpd service or daemon is running
 * - "public" is the community
 * - Only tested for SnmpV1
 * - IDE NetBeans 4.0
 * - JDK 1.5.0
 *
 * I've just followed the SnmpRequest.java program (which is part of
 * the snmp4j package, corresponding to the tools) to do this example
 */

package org.snmp4j.myExamples;

import org.snmp4j.*;
import org.snmp4j.smi.*;
import org.snmp4j.transport.DefaultUdpTransportMapping;
//import org.snmp4j.mp.*;

import java.io.IOException;
import java.util.Vector;

public class HelloWorldSNMP {
    // class members
    OctetString community = new OctetString( "public");
    Address address = new UdpAddress( "localhost/161");
    TransportMapping transport;
    Snmp snmp;
    Target target;
    Vector vbs = new Vector();

    /** Creates a new instance of HacerGetSNMPV1 */
    public HelloWorldSNMP() {
        // 1. create SNMP session
        try {
        transport = new DefaultUdpTransportMapping();
        snmp = new Snmp( transport );
        }
        catch ( IOException e )
        {
        }

        // 2. set the target which will be requested
        CommunityTarget targetX = new CommunityTarget();
        targetX.setCommunity( community );
        target = ( Target ) targetX;

        target.setVersion( 0 );
        target.setAddress( address );
        target.setRetries( 1 );
        target.setTimeout( 1000 );

        try {
            snmp.listen();
        }
        catch ( IOException e )
        {

        }

        // 3. create the PDU of the message. In this case a GET
        PDU request = new PDU();
        request.setType( -96 ); // honestly, I don't know yet why -96 ???
        // Answer: -96 == 0xA0 == PDU.GET

        //
        vbs.add( new VariableBinding( new OID("1.3.6.1.2.1.1.5.0" ) ) );

        //for ( int i = 0; i < vbs.size(); i++ )
            request.add( ( VariableBinding ) vbs.get(0 ) );

        // prepare to get the response of the agent
        PDU response = null;
        try {
            response = snmp.sendPDU( request, target);
            snmp.close();
        }
        catch ( IOException e )
        {
        }

        // 4. print output
        System.out.println( "Response received with requestID = " 	+
        	response.getRequestID() + " , errorIndex = " +
			response.getErrorIndex() + " , errorStatus = " +
        	response.getErrorStatus() );
        for ( int i = 0; i < response.size(); i++ )
        {
            VariableBinding vb = response.get( i );
            System.out.println( vb.toString() );
        }
    }

    public static void main( String args[] )   {
        System.out.println( "Hello World SNMP4J !!!");
        System.out.println( " The beginning !!! " );
        HelloWorldSNMP app = new HelloWorldSNMP();
        System.out.println( " Just finished !!!" );
    }
}

****************************** the output
Hello World SNMP4J !!!
 The beginning !!!
Exception in thread "main" java.lang.NullPointerException
	at org.snmp4j.myExamples.HelloWorldSNMP.<init>(HelloWorldSNMP.java:94)
	at org.snmp4j.myExamples.HelloWorldSNMP.main(HelloWorldSNMP.java:107)