The pcap dumper example expands on the classic example and creates a PcapDumper object which facilitates copying of captured packets to a file. This is exactly how packet dumping is done with native libpcap library as well.
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package org.jnetpcap.examples;
import java.io.File;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import org.jnetpcap.Pcap;
import org.jnetpcap.PcapDumper;
import org.jnetpcap.PcapHandler;
import org.jnetpcap.PcapIf;
public class PcapDumperExample {
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
/***************************************************************************
* First get a list of devices on this system
**************************************************************************/
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\n",
errbuf.toString());
return;
}
PcapIf device = alldevs.get(1); // We know we have atleast 1 device
/***************************************************************************
* Second we open up the selected device
**************************************************************************/
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: %s\n",
errbuf.toString());
return;
}
/***************************************************************************
* Third we create a PcapDumper and associate it with the pcap capture
***************************************************************************/
String ofile = "tmp-capture-file.cap";
PcapDumper dumper = pcap.dumpOpen(ofile); // output file
/***************************************************************************
* Fouth we create a packet handler which receives packets and tells the
* dumper to write those packets to its output file
**************************************************************************/
PcapHandler<PcapDumper> dumpHandler = new PcapHandler<PcapDumper>() {
public void nextPacket(PcapDumper dumper, long seconds, int useconds,
int caplen, int len, ByteBuffer buffer) {
dumper.dump(seconds, useconds, caplen, len, buffer);
}
};
/***************************************************************************
* Fifth we enter the loop and tell it to capture 10 packets. We pass
* in the dumper created in step 3
**************************************************************************/
pcap.loop(10, dumpHandler, dumper);
File file = new File(ofile);
System.out.printf("%s file has %d bytes in it!\n", ofile, file.length());
/***************************************************************************
* Last thing to do is close the dumper and pcap handles
**************************************************************************/
dumper.close(); // Won't be able to delete without explicit close
pcap.close();
if (file.exists()) {
file.delete(); // Cleanup
}
}
}
For more information please visit jNetPcap userguide.