Java网络模拟器入门

Question

我正在使用Java网络模拟器（JNS）模拟网络拓扑。我遵循了JNS下载文档中的教程。以下是示例的代码：

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();

    }
}

我面临的问题是，当我调用sim.run（）时，程序会向我抛出NullPointerException错误。我是JNS的新手。请指导我如何在上面代码的帮助下成功创建一个用于javis模拟的文件。我使用的是Eclipse IDE。提前谢谢。

Answer 1

尝试设置跟踪实例

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