Packet capture with Pcap4J in Groovy

Pcap4jLoop.groovy

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.core.PcapStat
import org.pcap4j.packet.Packet
import org.pcap4j.util.NifSelector

def filter
if (args) {
  filter = args[0]
}

def nif = new NifSelector().selectNetworkInterface()
if (!nif) {
  System.exit 1
}

def handle = nif.openLive 65536, PromiscuousMode.PROMISCUOUS, 10

if (filter) {
  handle.setFilter filter, BpfCompileMode.OPTIMIZE
}

def printPacket = { packet ->
  println "A packet captured at ${handle.getTimestamp()}:"
  println packet
}

def listener = new PacketListener() {
  void gotPacket(Packet packet) {
    printPacket packet
  }
}

handle.loop 5, listener