pcap4j+winpcap should I run rpcapd.exe manually? - winpcap

Question

Hi I have downloaded pcap4j and winpcap and all jar (jna, pcap4j-core-1.8.2, slf4j-api-1.7.25, slf4j-simple-1.7.25) dependency manually. Added to the project and all compile well.
BUT:
when I began to sniff packet.getHeader() and packet.getPayload() returns null!
if I run manually rpcapd.exe then it works...
why?
package sniffer;
import java.io.IOException;
import org.pcap4j.core.BpfProgram.BpfCompileMode;
import org.pcap4j.core.NotOpenException;
import org.pcap4j.core.PacketListener;
import org.pcap4j.core.PcapHandle;
import org.pcap4j.core.PcapNativeException;
import org.pcap4j.core.PcapNetworkInterface;
import org.pcap4j.core.PcapNetworkInterface.PromiscuousMode;
import org.pcap4j.packet.Packet;
import org.pcap4j.util.NifSelector;
public class App {
static PcapNetworkInterface getNetworkDevice() {
PcapNetworkInterface device = null;
try {
device = new NifSelector().selectNetworkInterface();
} catch (IOException e) {
e.printStackTrace();
}
return device;
}
public static void main(String[] args) throws PcapNativeException, NotOpenException {
// The code we had before
PcapNetworkInterface device = getNetworkDevice();
System.out.println("You chose: " + device);
// New code below here
if (device == null) {
System.out.println("No device chosen.");
System.exit(1);
}
// Open the device and get a handle
int snapshotLength = 65536; // in bytes
int readTimeout = 50; // in milliseconds
final PcapHandle handle;
handle = device.openLive(snapshotLength, PromiscuousMode.PROMISCUOUS, readTimeout);
String filter = "tcp port 80";
handle.setFilter(filter, BpfCompileMode.OPTIMIZE);
// Create a listener that defines what to do with the received packets
PacketListener listener = new PacketListener() {
#Override
public void gotPacket(Packet packet) {
// Override the default gotPacket() function and process packet
System.out.println(handle.getTimestamp());
System.out.println(packet);
System.out.println(packet.getHeader());///////////////<<<<<<<<<<<------------
}
};
// Tell the handle to loop using the listener we created
try {
int maxPackets = 50;
handle.loop(maxPackets, listener);
} catch (InterruptedException e) {
e.printStackTrace();
}
// Cleanup when complete
handle.close();
}
}

Answer 1

You need to add a packet factory (e.g. pcap4j-packetfactory-static.jar) to your classpath, or Pcap4J creates UnknownPacket instances, getPayload() and getHeader() of which return null, for all packets.