-- Possible call
-- ./PingTimeServers time.nist.gov time-a.nist.gov time.ien.it
-- NB: It is explicitly disallowed to ask a NIST time server for time 
-- more frequently than once every 4 seconds.


module PingTimeServers where

import POSIX
import Data.Functional.List

port = Port 13  -- standard port for time servers

client neterror report sock = class

    established = action
       sock.inFile.installR report

    close = request result ()

    result Connection {..}
 
struct Pinger where
    report :: Int -> String -> Action
    finish :: Action

pinger args print quit = class

    outstanding := args

    report i mess = action
       outstanding := delete i outstanding
       print i mess
       if (null outstanding) then quit
    
    finish = action
      forall i <- outstanding do 
        print i "no response"
      quit

    result Pinger {..}


root w = class
   env = new posix w
   args = [1..size env.argv-1] 
   print i mess = env.stdout.write (env.argv!i ++ ": "++ mess ++ "\n")

   p = new pinger args print (env.exit 0)
       
   result action
      forall i <- args do
         env.inet.tcp.connect (Host (env.argv!i)) port (client (p.report i) (p.report i))
      after (sec 2) send p.finish