Ho to decrypt snmp log using Snmp4j

Question

Hi all
I have problem with decoding snmp log using my own listener.
From the sample inside the snmp4j source code, what i can see here is we have to use their listener.
Because of this, the snmp4j listener cannot bind the port 162 because my program has bound it.
What is another way for me to get the the real snmp log(not encrypted).
Below are the code of my snmparser that has problem to bind the port
public class SnmpParser extends Parser implements CommandResponder {
private String[] data = (String[]) COLUMN_DEFAULT_VALUE.clone();
private String strLog = "";
private String strIP = "";
private MultiThreadedMessageDispatcher dispatcher;
private Snmp snmp = null;
private Address listenAddress;
private ThreadPool threadPool;
private int n = 0;
private long start = -1;
private ByteBuffer bis = null;
private TransportMapping transport = null;
public SnmpParser(String strIP, String strRawlog) {
this.strIP = strIP;
strLog = strRawlog;
private void init() throws UnknownHostException, IOException {
threadPool = ThreadPool.create("Trap", 2);
dispatcher =
new MultiThreadedMessageDispatcher(threadPool,
new MessageDispatcherImpl());
listenAddress =
GenericAddress.parse(System.getProperty("snmp4j.listenAddress",
"udp:192.168.2.55/162")); //This 162 port caused proggram terminated because cannot bind
if (listenAddress instanceof UdpAddress) {
transport = new DefaultUdpTransportMapping((UdpAddress)listenAddress);
else {
transport = new DefaultTcpTransportMapping((TcpAddress)listenAddress);
snmp = new Snmp(dispatcher,transport);
snmp.getMessageDispatcher().addMessageProcessingModel(new MPv1());
snmp.getMessageDispatcher().addMessageProcessingModel(new MPv2c());
snmp.getMessageDispatcher().addMessageProcessingModel(new MPv3());
USM usm = new USM(SecurityProtocols.getInstance(),
new OctetString(MPv3.createLocalEngineID()), 0);
SecurityModels.getInstance().addSecurityModel(usm);
// snmp.listen();
public void doConvert() {
System.out.println("Rawlog : " strLog);
+//System.out.println("Rawlog(hex) : "+ new OctetString(strLog).toHexString());
try {
init();
snmp.addCommandResponder(this);
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
//fire ProcessMessage
bis = ByteBuffer.wrap(strLog.getBytes());
try {
if(transport!=null) {
((DefaultUdpTransportMapping)transport).fireProcessMessage(new UdpAddress(InetAddress.getByName("192.168.2.55"),
162), bis);
System.out.println("Firing");
} else {
System.out.println("Not firing");
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
public void processPdu(CommandResponderEvent event) {
System.out.println(event.getPDU());
System.out.println(event.getPDU().getVariableBindings());
System.out.println(event.getPDU().getType());
Below is just my listener code
public final class UDPListener extends Listener {
private int iUDPPort = 0;
private boolean bStop = false;
private byte[] buffer = null;
private DatagramSocket dSocket = null;
private DatagramPacket dPacket = null;
public UDPListener(int piUDPPort) {
this.iUDPPort = piUDPPort;
this.buffer = new byte[1024];
private boolean exceptionCaught = false;
public UDPListener(int piUPDPort, int piBufferSize) {
this.iUDPPort = piUPDPort;
this.buffer = new byte[piBufferSize];
public void run() {
// if UDP listener initialized successfully, proceed with listening
// or else exit this thread
if (initUDPListener()) {
Indefinite loop while bStop remains false. bStop is only set in 2 places.
1. when stopListener method is called
*2. when an exception is encountered in the block*
while (!bStop) {
try {
dSocket.receive(dPacket);
extractLog();
} catch (Exception e) {
Signifying exception is caught. Ending loop
Logger.getLogger(UDPListener.class).error("Error while listening to UDP port: " + iUDPPort, e);
exceptionCaught = true;
bStop = true;
try {
if (dSocket != null)
dSocket.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (exceptionCaught)
ListenerThreadReviver.getInstance().reinitListener("UDP", iUDPPort);
Logger.getLogger(UDPListener.class).debug("UDPListener exiting gracefully");
private void extractLog() {
String strLog = "";
String strDeviceIP = "";
strLog = new String(dPacket.getData(), 0, dPacket.getLength());
strDeviceIP = dPacket.getAddress().toString().replace("/", "");
processLog(strLog, strDeviceIP);
dPacket.setLength(buffer.length);
private boolean initUDPListener() {
try {
// constructs a datagram socket and binds it to the specified port on the local host machine
dSocket = new DatagramSocket(iUDPPort);
// constructs a new datagram packet for receiving packets
dPacket = new DatagramPacket(buffer, buffer.length);
catch (SocketException e)
// if the socket could not be opened, or the socket could not bind to the specified local port.
e.printStackTrace();
// attempts to close dSocket if it is open
if (dSocket != null && !dSocket.isClosed()) {
dSocket.close();
// returns false to indicate initialization failure
return false;
return true;
public synchronized void stopListener() {
bStop = true;
dSocket.close();
-----

Answer 1

instead of using  SNMPv2-SMI::mib-2.16.19.12.0  use the actual OID.
i believe you can set it like this ipRouteNextHop.0.0.0.0 a X.X.X.X
http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?objectInput=.1.3.6.1.2.1.4.21.1.7+&translate=Translate&submitValue=SUBMIT