使用jnetpcap进行数据使用计数

Question

I have written the following code for a program which could measure the total data usage of the computer. I have used the method getTotalSize() of the class PcapPacket. Is it directly indicative of the data usage (if added continuously) or should I use some other method.

import org.jnetpcap.packet.PcapPacket; 
import org.jnetpcap.protocol.JProtocol; 

public class CapturePacket{

public static void main(String[] args) throws Exception {
    List<PcapIf> alldevs = new ArrayList<PcapIf>(); // Will be filled with
    // NICs
    StringBuilder errbuf = new StringBuilder(); // For any error msgs


    int r = Pcap.findAllDevs(alldevs, errbuf);
    if (r == Pcap.NOT_OK || alldevs.isEmpty()) {
        System.err.printf("Can't read list of devices, error is %s", errbuf
                .toString());
        return;
    }
    PcapIf device = (PcapIf) alldevs.get(0); // We know we have at least 1 device


    String ad = device.getHardwareAddress().toString();
    System.out.println("\nCurrently open adapter MAC:" + ad);

    int snaplen = 64 * 1024; // Capture all packets, no truncation
    int flags = Pcap.MODE_PROMISCUOUS; // capture all packets
    int timeout = 10; //10*1000; // No timeout, non-interactive traffic
    final Pcap pcap = Pcap.openLive(device.getName(), snaplen, flags, timeout,
            errbuf);
    if (pcap == null) {
        System.err.printf("Error while opening device for capture: "
                + errbuf.toString());
        return;
    }


    PcapPacketHandler<String> jpacketHandler = new PcapPacketHandler<String>() 
     {
         long total_traffic = 0,count = 0;
         int i;


     public void nextPacket(PcapPacket packet, String user) {

         count += packet.getTotalSize();
         if( count>1048576 )
            {
                i++;
                total_traffic += count;
             System.out.println(i+"MB"+"\t total:"+total_traffic);
             count=count-1048576;

            }
     };
     };           
            pcap.loop(-1,jpacketHandler," ");  
            pcap.close(); 
            }

}

The above is a code I've written in an attempt to count the traffic passing through the network. Is it directly indicative (if not perfectly accurate) of the data usage of the computer?

Answer 1

You should use packet.getPacketWirelen() According to the documentation, it gets the original length as seen on the wire, even if the captured packet is truncated.

Additionally you should check if the packet is from or to your internal network only, so then it shouldn't count towards your data usage(I'm assuming you want data usage as seen by your ISP).

After that it should be indicative of your data usage.