[SNMP4J] java.lang.NullPointerException: Context engine ID must not be null

[FLORENT Philippe]

Hello everyone,


-          Doing a get on some OID  give me "unkown instance" although they work with snmpwalk on the command line and GET works with mib explorer



-          So I try to implement an snmp walk in snmp4j but I keep getting that error

Here is the code

I tried to use request.getContextEngineID(), but it is also null

public class SnmpProber
{
   private Snmp snmp;
    private UserTarget target;

    private byte[] authEngineId0=null;

    public SnmpProber(String ipAddress,String port,String userName,String authPass,String privPass)
    {
        try
        {
            Address targetAddress = GenericAddress.parse("udp:"+ipAddress+"/"+port);
            TransportMapping transport = new DefaultUdpTransportMapping();
            snmp = new Snmp(transport);
            USM usm = new USM(SecurityProtocols.getInstance(),new OctetString(MPv3.createLocalEngineID()), 0);
            SecurityModels.getInstance().addSecurityModel(usm);
            transport.listen();

            target = new UserTarget();
            target.setAddress(targetAddress);
            target.setRetries(1);
            target.setTimeout(5000);
            target.setVersion(SnmpConstants.version3);
            target.setSecurityLevel(SecurityLevel.AUTH_PRIV);
            target.setSecurityName(new OctetString(userName));

            authEngineId0 = snmp.discoverAuthoritativeEngineID(target.getAddress(), 5000);

            if(authEngineId0==null)
                System.out.println("cannot connect");
            else
            {
                // add user to the USM
                UsmUser usmUser=new UsmUser(new OctetString(userName),
                                      AuthSHA.ID,
                                      new OctetString(authPass),
                                      PrivAES128.ID,
                                      new OctetString(privPass));

                snmp.getUSM().addUser(new OctetString("v3DefaultUser"),
                                      new OctetString(authEngineId0),
                                      usmUser);
            }
        } catch (IOException ex) {
            Logger.getLogger(SnmpProber.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public boolean isOk()
    {
        return authEngineId0!=null;
    }

    class WalkCounts {
        public int requests;
        public int objects;
    }

    public List<VariableBinding> walk(String oid)
    {
        final List<VariableBinding> result;
        result = new LinkedList<VariableBinding>();
        ScopedPDU request;
        request = new ScopedPDU();
        request.setType(PDU.GETNEXT);

        request.add(new VariableBinding(new OID(oid)));

        request.setNonRepeaters(0);

        OID rootOID = request.get(0).getOid();

        final WalkCounts counts = new WalkCounts();
        final long startTime = System.currentTimeMillis();
        TreeUtils treeUtils = new TreeUtils(snmp, new DefaultPDUFactory());

        TreeListener treeListener = new TreeListener()
        {
            public boolean next(TreeEvent e) {
                counts.requests++;

                if (e.getVariableBindings() != null) {
                    VariableBinding[] vbs = e.getVariableBindings();
                    counts.objects += vbs.length;
                    for (int i = 0; i < vbs.length; i++) {
                        if (result != null) {
                            result.add(vbs[i]);
                        }
                        System.out.println(vbs[i].toString());
                    }
                }
                return true;
            }

            @Override
            public void finished(TreeEvent e) {
                if ((e.getVariableBindings() != null)
                        && (e.getVariableBindings().length > 0)) {
                    next(e);
                }

                System.out.println("Total requests sent:    "+ counts.requests);
                System.out.println("Total objects received: "+ counts.objects);
                System.out.println("Total walk time:        "+ (System.currentTimeMillis() - startTime)+ " milliseconds");

                if (e.isError()) {
                    System.err.println("The following error occurred during walk:");
                    System.err.println(e.getErrorMessage());
                }
                synchronized (this) {
                    this.notify();
                }
            }

            @Override
            public boolean isFinished() {
                return true;
            }
        };

        synchronized (treeListener)
        {
            treeUtils.getSubtree(target, rootOID, null, treeListener);  <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< exception here
            try
            {
                treeListener.wait();
            }
            catch (InterruptedException ex)
            {
                System.out.println("Tree retrieval interrupted: "+ex);
                Thread.currentThread().interrupt();
            }
        }

        return result;
    }

    public void Release()
    {
        try {
            snmp.close();
        } catch (IOException ex) {
            Logger.getLogger(SnmpProber.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}