Agent.java

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

import org.snmp4j.CommandResponder;
import org.snmp4j.CommandResponderEvent;
import org.snmp4j.CommunityTarget;
import org.snmp4j.MessageException;
import org.snmp4j.PDU;
import org.snmp4j.Snmp;
import org.snmp4j.Target;
import org.snmp4j.mp.StateReference;
import org.snmp4j.mp.StatusInformation;
import org.snmp4j.smi.*;
import org.snmp4j.transport.DefaultUdpTransportMapping;

public class Agent {

    public static void main(String[] args){
        try {
            UdpAddress udp = new UdpAddress("localhost/41265");
            DefaultUdpTransportMapping transport = new DefaultUdpTransportMapping(udp);
            Snmp snmp = new Snmp(transport);
            snmp.addCommandResponder(new CommandResponder() {

                @Override
                public void processPdu(CommandResponderEvent event) {
                    PDU pdu = event.getPDU();
                    PDU response = new PDU();
                    VariableBinding var = new VariableBinding(pdu.get(0).getOid());
                    var.setVariable(new Counter32(123));
                    response.add(var);
                    response.setType(PDU.RESPONSE);
                    System.out.println("Made response PDU: "+ response.toString());

                    //============== send response

                    try {
                        if (response.getBERLength() > event.getMaxSizeResponsePDU()) {
                            // response is tooBig
                            if (response.getType() != PDU.REPORT) {
                                if (event.getPDU().getType() == PDU.GETBULK) {
                                    while ((response.size() > 0) &&
                                       (response.getBERLength() >
                                        event.getMaxSizeResponsePDU()))
                                    {
                                        response.trim();
                                    }
                                }
                                else {
                                    response.clear();
                                    response.setRequestID(event.getPDU().getRequestID());
                                    response.setErrorStatus(PDU.tooBig);
                                }
                            }
                            if (response.getBERLength() > event.getMaxSizeResponsePDU()) {
                                //still too big and can't send a response
                                return;
                            }
                        }

                        StatusInformation status = new StatusInformation();
                        StateReference stateRef = event.getStateReference();
                        if (stateRef == null) {
                            System.out.println("No state reference available for event="+
                            event+". Cannot return response="+response);
                        }
                        else {
                            stateRef.setTransportMapping(event.getTransportMapping());
                            int resp = event.getMessageDispatcher().returnResponsePdu(event.getMessageProcessingModel(),
                                           event.getSecurityModel(),
                                           event.getSecurityName(),
                                           event.getSecurityLevel(),
                                           response,
                                           event.getMaxSizeResponsePDU(),
                                           stateRef,
                                           status);
                        }
                    }
                    catch (MessageException ex) {
                        System.out.println("Failed to send response to request "+event);
                    }

                    //=============end send response

                    // TODO Auto-generated method stub
                }
            });

        snmp.listen();
        }
        catch (Exception e){
        }

        while(true){
            //Now we play the waiting game
        }
    }
}