Java Network Simulator Getting Started

Question

I am working on simulating a network topology with Java Network Simulator(JNS). I have followed the tutorial which is in documentation of JNS download. Following is the code of the example:

package simulator_;
import java.awt.peer.TextComponentPeer;
import java.io.IOException;

import jns.Simulator;
import jns.element.DuplexInterface;
import jns.element.DuplexLink;
import jns.element.Interface;
import jns.element.Link;
import jns.element.Node;
import jns.trace.Event;
import jns.trace.Trace;
import jns.util.IPAddr;

public class simu {

    public static void main(String[] args) {
        Simulator sim=Simulator.getInstance();

        Node src=new Node("Source node");
        Node router=new Node("Router");
        Node dest=new Node("Destination node");
        sim.attach(src);
        sim.attach(router);
        sim.attach(dest);


        Interface src_iface=new DuplexInterface(new IPAddr(192,168,1,10));
        src.attach(src_iface);
        sim.attach(src_iface);

        Interface dest_iface=new DuplexInterface(new IPAddr(128,116,11,20));
        dest.attach(dest_iface);
        sim.attach(dest_iface);


        Interface route_iface192=new DuplexInterface(new IPAddr(192,168,1,1));
        Interface route_iface128=new DuplexInterface(new IPAddr(128,116,11,1));

        router.attach(route_iface192);
        router.attach(route_iface128);

        sim.attach(route_iface192);
        sim.attach(route_iface128);


        Link link_src_router=new DuplexLink(1000000,0.001);
        Link link_router_dest=new DuplexLink(64000,0.1);

        src_iface.attach(link_src_router,true);
        route_iface192.attach(link_src_router,true);
        sim.attach(link_src_router);

        route_iface128.attach(link_router_dest,true);
        dest_iface.attach(link_router_dest,true);
        sim.attach(link_router_dest);


        src.addDefaultRoute(src_iface);
        dest.addDefaultRoute(dest_iface);

        router.addRoute(new IPAddr(192,168,1,0),new IPAddr(255,255,255,0),
                        route_iface192);
        router.addRoute(new IPAddr(128,116,11,0),new IPAddr(255,255,255,0),
                        route_iface128);

        sim.run();


    }

}

The problem I am facing is when I call sim.run(), the program throws me NullPointerException error. I am a newbie in JNS. Kindly guide if how can I successfully create a file foe javis to Simulate with the help of above code. I am using Eclipse IDE. Thanks in advance.

Have a look at the stack trace of the NullPointerException. What line of your code appears in the stack trace? — Eamonn O'Brien-Strain
– Eamonn O'Brien-Strain, Commented Feb 28, 2015 at 20:00

spy · Accepted Answer · 2015-02-28 19:56:58Z

1

try setting a trace instance

sim.setTrace(new JavisTrace("output.txt"));

answered Feb 28, 2015 at 19:56

spy

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