PeerUnavailableException using JAIN SIP API and NIST implementation

I am trying to create a simple SIP application using JAIN SIP 1.2 and a NIST implementation. I am using JavaSE1.7 with Eclipse as my IDE. Problem: I get javax.sip.PeerUnavailableableException when trying to build a SipStack object.

My main class:

package net.bezeqint.sip.enp;

public class ListenerMain {

    public static void main(String[] args) {

        try {
            System.out.println("Creating ExampleListener...");
            ExampleListener listener = new ExampleListener();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    }
}

My problem class (the one from which I am building the SIP Stack object):

package net.bezeqint.sip.enp;

import javax.sip.*;
import javax.sip.message.*;
import javax.sip.header.*;
import javax.sip.address.*;
import javax.sip.address.URI;

import java.net.*;
import java.util.*;

public class ExampleListener implements SipListener {

    private SipFactory mySipFactory;
    private SipStack mySipStack;
    private ListeningPoint myListeningPoint;
    private SipProvider mySipProvider;
    private MessageFactory myMessageFacory;
    private HeaderFactory myHeaderFactory;
    private AddressFactory myAddressFactory;
    private Properties myProperties;
    private String myIP;
    private int myPort = 5060;

    public ExampleListener() throws Exception {

        mySipFactory = SipFactory.getInstance();
        mySipFactory.setPathName("gov.nist");

        // create factories
        myMessageFacory = mySipFactory.createMessageFactory();
        myHeaderFactory = mySipFactory.createHeaderFactory();
        myAddressFactory = mySipFactory.createAddressFactory();
        // create a Properties object to pass as an argument to the createSipStack() method
        myProperties = new Properties();
        myProperties.setProperty("javax.sip.STACK_NAME","myStack");
        // test
        // myProperties.setProperty("javax.sip.IP_ADDRESS","192.168.1.1");

        System.out.println("Creating SipStack...");
        mySipStack = mySipFactory.createSipStack(myProperties);
        System.out.println("SipStack created!");

        // get our IP address to be used when creating the ListeningPoint
        myIP = InetAddress.getLocalHost().getHostAddress();

        myListeningPoint = mySipStack.createListeningPoint(myIP, myPort, "udp");

        mySipProvider = mySipStack.createSipProvider(myListeningPoint);

        mySipProvider.addSipListener(this);


        // begin building a request
        Address destAddress = myAddressFactory.createAddress("sip:registrar.ocean.com");
        Address addressOfRecord = myAddressFactory.createAddress("sip:peter@ocean.com");
        Address contactAddress = myAddressFactory.createAddress("sip:peter@169.254.153.60");

        // convert address to URI object
        URI myRequestURI = destAddress.getURI();

        // create headers
        ArrayList viaHeaders = new ArrayList();
        ViaHeader myViaHeader = myHeaderFactory.createViaHeader("Peterpc.ocean.com"
                , 5060, "udp", "z9hG4bKnashds7");
        viaHeaders.add(myViaHeader);

        MaxForwardsHeader myMaxForwardsHeader =
                myHeaderFactory.createMaxForwardsHeader(70);

        ToHeader myToHeader = myHeaderFactory.createToHeader(addressOfRecord, null);

        FromHeader myFromHeader = myHeaderFactory.createFromHeader(addressOfRecord, "456248");

        CallIdHeader myCallIDHeader = myHeaderFactory.createCallIdHeader("843817637684230@998sdasdh09");

        CSeqHeader myCseqHeader = myHeaderFactory.createCSeqHeader(1826, "REGISTER");

        // create message
        Request myRequest = myMessageFacory.createRequest(myRequestURI, "REGISTER", myCallIDHeader, myCseqHeader, myFromHeader, myToHeader, viaHeaders, myMaxForwardsHeader);

        // add missing headers
        ContactHeader myContactHeader = myHeaderFactory.createContactHeader(contactAddress);
        myRequest.addHeader(myContactHeader);

        // print the message
        System.out.println(myRequest);

    }

    @Override
    public void processDialogTerminated(DialogTerminatedEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void processIOException(IOExceptionEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void processRequest(RequestEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void processResponse(ResponseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void processTimeout(TimeoutEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void processTransactionTerminated(TransactionTerminatedEvent arg0) {
        // TODO Auto-generated method stub

    }
}

Console output:

ExampleListener...      SipStack...     javax.sip.PeerUnavailableException: SIP: gov.nist.javax.sip.SipStackImpl . , .          javax.sip.SipFactory.createStack(SipFactory.java:324)          javax.sip.SipFactory.createSipStack(SipFactory.java:152)          net.bezeqint.sip.enp.ExampleListener. (ExampleListener.java:41)         at net.bezeqint.sip.enp.ListenerMain.main(ListenerMain.java:9)     : java.lang.reflect.InvocationTargetException         at sun.reflect.NativeConstructorAccessorImpl.newInstance0 ( )         at sun.reflect.NativeConstructorAccessorImpl.newInstance( )         at sun.reflect.DelegatingConstructorAccessorImpl.newInstance( )          java.lang.reflect.Constructor.newInstance( )          javax.sip.SipFactory.createStack(SipFactory.java:314)         ... 3     : java.lang.NoClassDefFoundError: org/apache/log4j/          gov.nist.javax.sip.SipStackImpl. (SipStackImpl.java:387)         ... 8     : java.lang.ClassNotFoundException: org.apache.log4j.Priority          java.net.URLClassLoader $1.run( )          java.net.URLClassLoader $1.run( )          java.security.AccessController.doPrivileged( )         at java.net.URLClassLoader.findClass( )          java.lang.ClassLoader.loadClass( )         at sun.misc.Launcher $AppClassLoader.loadClass( )          java.lang.ClassLoader.loadClass( )         ... 9

, mySipFactory.createSipStack(), , .

javax.sip.PeerUnavailableException?