JNetPcap捕获包未返回IP

Question

我在这里有这段代码https://javatutorial.net/capture-network-packages-java，但是它没有返回src或目标ip。我可以通过

            System.out.println("packet.getHeader(ip)");
            System.out.println(packet.getHeader(ip));

Ip：* Ip4 - "ip版本4“- offset=14 (0xE) length=20协议suite=NETWORK

Ip地址：

Ip:版本=4

Ip: hlen =5 5*4= 20字节，无Ip选项

Ip: diffserv = 0x0 (0)

Ip: 0000 00..=代码点:未设置

Ip：......0。= ECN位:未设置

Ip：.......0 =ECE位:未设置

Ip:长度= 137

Ip: id = 0xC22C (49708)

Ip:标志= 0x2 (2)

Ip: 0..=保留

Ip：.1。=1 DF:不分段:设置

Ip：..0 = MF:更多片段:未设置

Ip:偏移量=0

Ip: ttl = 62生存时间

Ip: type =6下一步:传输控制

Ip:校验和= 0xF22E (61998)正确

Ip:来源= 10.222.82.222

Ip:目的地址= 10.222.82.224

Ip地址：

我做错了什么？

`import java.util.ArrayList;
 import java.util.List;
 import org.jnetpcap.Pcap;
 import org.jnetpcap.PcapIf;
 import org.jnetpcap.packet.PcapPacket;
 import org.jnetpcap.packet.PcapPacketHandler;
 import org.jnetpcap.protocol.network.Ip4;
public class PackageCapture {
public static void main(String[] args) {
    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.OK || alldevs.isEmpty()) {
        System.err.printf("Can't read list of devices, error is %s",
                errbuf.toString());
        return;
    }
    System.out.println("Network devices found:");
    int i = 0;
    for (PcapIf device : alldevs) {
        String description = (device.getDescription() != null) ? device
                .getDescription() : "No description available";
        System.out.printf("#%d: %s [%s]\n", i++, device.getName(),
                description);
    }
    PcapIf device = alldevs.get(0); // Get first device in list
    System.out.printf("\nChoosing '%s' on your behalf:\n",
            (device.getDescription() != null) ? device.getDescription()
                    : device.getName());
    int snaplen = 64 * 1024; // Capture all packets, no trucation
    int flags = Pcap.MODE_PROMISCUOUS; // capture all packets
    int timeout = 10 * 1000; // 10 seconds in millis
    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>() {
        public void nextPacket(PcapPacket packet, String user) {
            byte[] data = packet.getByteArray(0, packet.size()); // the package data
            byte[] sIP = new byte[4];
            byte[] dIP = new byte[4];
            Ip4 ip = new Ip4();
            if (packet.hasHeader(ip) == false) {
                return; // Not IP packet
            }
            ip.source(sIP);
            ip.destination(dIP);
            /* Use jNetPcap format utilities */
            String sourceIP = 
     org.jnetpcap.packet.format.FormatUtils.ip(sIP);
                String destinationIP = 
     org.jnetpcap.packet.format.FormatUtils.ip(dIP);

            System.out.println("srcIP=" + sourceIP + 
                    " dstIP=" + destinationIP + 
                    " caplen=" + packet.getCaptureHeader().caplen());
        }
    };
    // capture first 10 packages
    pcap.loop(10, jpacketHandler, "jNetPcap");
    pcap.close();
}
}`

Answer 1

非常简单，他们修改了代码。而不是

ip.source(sIP)；ip.destination(dIP)；

做

sIP = ip.source()；dIP = ip.destination()；