script.scala

import scala.io.Source

val seqr = """.*:(.*\..*)\sIP.*seq\s[0-9]+?:(.+?),""".r
val ackr = """.*:(.*\..*)\sIP.*?Flags\s\[\.\],\sack\s(.+?),\swin.*""".r
if(args.length > 0) {
  val lines = Source.fromFile(args(0)).getLines().toList

  val seqs = for {
    line <- lines
    seq <- seqr.findFirstMatchIn(line)
  } yield List(seq.group(1),seq.group(2))

  val tmps = for {
    line <- lines
    ack <- ackr.findFirstMatchIn(line)
  } yield List(ack.group(1),ack.group(2))

  val acks = for {
    i <- 0 until tmps.length -1 
    if tmps(i)(1) != tmps(i+1)(1) 
  } yield List(tmps(i)(0),tmps(i)(1))

  val time = for {
    seq <- seqs
    ack <- acks
    if seq(1) == ack(1)
  } yield ack(0).toDouble - seq(0).toDouble

  println("average = " + time.sum/time.length)
}
else Console.err.println("Please enter inputfile")