code: package cic.cs.unb.ca.jnetpcap.worker;
  
  import cic.cs.unb.ca.jnetpcap.BasicFlow;
  import cic.cs.unb.ca.jnetpcap.FlowGenerator;
  import cic.cs.unb.ca.jnetpcap.PacketReader;
  import org.jnetpcap.Pcap;
  import org.jnetpcap.nio.JMemory.Type;
  import org.jnetpcap.packet.PcapPacket;
  import org.jnetpcap.packet.PcapPacketHandler;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.swing.*;
  import java.util.List;
  
  public class TrafficFlowWorker extends SwingWorker<String,String> implements FlowGenListener{
  
  	public static final Logger logger = LoggerFactory.getLogger(TrafficFlowWorker.class);
      public static final String PROPERTY_FLOW = "flow";
  	private String device;
  
  
      public TrafficFlowWorker(String device) {
  		super();
  		this.device = device;
  	}
  
  	@Override
  	protected String doInBackground() {
  		
  		FlowGenerator   flowGen = new FlowGenerator(true,120000000L, 5000000L);
  		flowGen.addFlowListener(this);
  		int snaplen = 64 * 1024;//2048; // Truncate packet at this size
  		int promiscous = Pcap.MODE_PROMISCUOUS;
  		int timeout = 60 * 1000; // In milliseconds
  		StringBuilder errbuf = new StringBuilder();
  		Pcap pcap = Pcap.openLive(device, snaplen, promiscous, timeout, errbuf);
  		if (pcap == null) {
  			logger.info("open {} fail -> {}",device,errbuf.toString());
  			return String.format("open %s fail ->",device)+errbuf.toString();
  		}
  
  		PcapPacketHandler<String> jpacketHandler = (packet, user) -> {
  
              /*
               * BufferUnderflowException while decoding header
               * that is because:
               * 1.PCAP library is not multi-threaded
               * 2.jNetPcap library is not multi-threaded
               * 3.Care must be taken how packets or the data they referenced is used in multi-threaded environment
               *
               * typical rule:
               * make new packet objects and perform deep copies of the data in PCAP buffers they point to
               *
               * but it seems not work
               */
  
              PcapPacket permanent = new PcapPacket(Type.POINTER);
              packet.transferStateAndDataTo(permanent);
  
              flowGen.addPacket(PacketReader.getBasicPacketInfo(permanent, true, false));
              if(isCancelled()) {
                  pcap.breakloop();
                  logger.debug("break Packet loop");
              }
          };
  
          //FlowMgr.getInstance().setListenFlag(true);
          logger.info("Pcap is listening...");
          firePropertyChange("progress","open successfully","listening: "+device);
          int ret = pcap.loop(Pcap.DISPATCH_BUFFER_FULL, jpacketHandler, device);
  
  		String str;
          switch (ret) {
              case 0:
                  str = "listening: " + device + " finished";
                  break;
              case -1:
                  str = "listening: " + device + " error";
                  break;
              case -2:
                  str = "stop listening: " + device;
                  break;
                  default:
                      str = String.valueOf(ret);
          }
  
          return str;
  	}
  
  	@Override
  	protected void process(List<String> chunks) {
  		super.process(chunks);
  	}
  
  	@Override
  	protected void done() {
  		super.done();
  	}
  
  	@Override
  	public void onFlowGenerated(BasicFlow flow) {
          firePropertyChange(PROPERTY_FLOW,null,flow);
  	}
  }
  