Packet capture with Pcap4J in Kotlin

Pcap4jLoop.kt

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

fun PcapHandle.printLoop(count: Int) {
  loop(count, {packet: Packet ->
    println("A packet captured at ${getTimestamp()}:")
    println(packet)
  })
}

fun main(args: Array<String>) {
  val filter = if (args.size != 0) args[0] else null

  val nif = NifSelector().selectNetworkInterface()
  nif ?: System.exit(1)

  val handle = nif.openLive(65536, PromiscuousMode.PROMISCUOUS, 10)

  filter?.let {
    if (filter.length != 0) {
      handle.setFilter(filter, BpfCompileMode.OPTIMIZE)
    }
  }

  handle.printLoop(count = 5)
}