static void killPortAndWait(int port) {
  killPortAndWait("localhost", port);
}

static void killPortAndWait(S ip, int port) ctex {
  print("Sending kill switch to " + ip + ":" + port);
  DialogIO io = talkTo(ip, port);
  io.sendLine("kill!");
  try {
    // wait until it is closed from other side
    S s;
    while ((s = io.readLine()) != null)
      print(port + "< " + s);
  } catch (Exception e) {}
  io.close(); // never throws exceptions
}