# 使用 Java 捕获网络数据包 > 原文： [https://javatutorial.net/capture-network-packages-java](https://javatutorial.net/capture-network-packages-java) 该示例演示了如何使用 pcap 和 Java 捕获网络数据包。 要运行示例，您将需要为操作系统安装 libpcap 。 对于 Windows，下载并安装 [WinPcap](https://www.winpcap.org/install/) 。 Ubuntu 用户可以运行以下命令来安装 libpcap： ```java sudo apt-get install libpcap-dev ``` 我们将使用 [jNetPcap](https://sourceforge.net/projects/jnetpcap/) 作为 Java 包装器。 以下示例要求版本 1.4 ## 列出网络设备 ```java import java.util.ArrayList; import java.util.List; import org.jnetpcap.Pcap; import org.jnetpcap.PcapIf; public class NetworkInterfaces { 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.NOT_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); } } } ``` ## 捕捉数据包 以下完整示例捕获了前 10 个数据包： ```java 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(); } } ``` 如果要捕获特定的数据包，可以设置一个过滤器，如下所示： ```java PcapBpfProgram filter = new PcapBpfProgram(); String expression = "tcp port 3724 or tcp port 1119"; int optimize = 0; // 0 = false int netmask = 0xFFFFFF00; // 255.255.255.0 if (pcap.compile(filter, expression, optimize, netmask) != Pcap.OK) { System.err.println(pcap.getErr()); return; } if (pcap.setFilter(filter) != Pcap.OK) { System.err.println(pcap.getErr()); return; } ```