import java.io.*;   
import java.net.*;   
import java.util.*;   
   
public class PingClient {   
    private static long returnTime;   
    private static int returnSeq;   
      
    public static void main(String[] args)throws Exception {   
      if (args.length != 2) { 
         System.out.println("Required arguments: host port");   
         return;   
       }   
       String host = args[0];   
       int port = Integer.parseInt(args[1]);      
  
       DatagramSocket socket = new DatagramSocket();   
       socket.setSoTimeout(1000);   
       InetAddress serverAddress = InetAddress.getByName(host);   
       byte[] sendData = new byte[1024];   
       byte[] receiveData = new byte[1024];   
      
       for(int i = 0; i < 10; i++) {   
       	String clientMess = "PING ";   
       	Long tstamp = new Long(System.currentTimeMillis());   
       	clientMess += (new Integer(i).toString()) + " ";   
       	clientMess += ( tstamp.toString() + " \r\n" );   
       	sendData = clientMess.getBytes();   
       	DatagramPacket sendPacket =    
       		new DatagramPacket(sendData,clientMess.length(),serverAddress,port);   
       	socket.send(sendPacket);   

       	DatagramPacket request = new DatagramPacket(new byte[1024], 1024);   
       	try {                   
       		socket.receive(request);   
       		parseReply(request);                      

       		if (! checkSequence(returnSeq,i)) {   
       			System.out.print("received out of order packet");   
       		}   
       		printData(request);   
       	} catch(SocketTimeoutException e) {   
       		System.out.println("Error: recieve timed out");   
       	}   
       }   
    }   
   
    private static void printData(DatagramPacket request) throws Exception {   
       long currentTime = System.currentTimeMillis();   
       long rtt = currentTime - returnTime;   
       System.out.println(   
               "Received from " + request.getAddress().getHostAddress() +    
               ": " + returnSeq + ":" + returnTime + "elapsed: " + rtt);   
    }   

    private static boolean checkSequence(int returnSeq, int packetNumber) {   
      if (returnSeq != packetNumber)   
        return false;   
      else    
        return true;              
    }   
   
    private static void parseReply(DatagramPacket request) throws Exception {   
       byte[] buf = request.getData();          
       ByteArrayInputStream bais = new ByteArrayInputStream(buf);   
       InputStreamReader isr = new InputStreamReader(bais);   
       BufferedReader br = new BufferedReader(isr);   
         
       String line = br.readLine();   
       String resp[] = line.split(" ");   
       System.out.println("sequence = " + resp[1]);   
       returnSeq = Integer.parseInt(resp[1]);   
       System.out.println("ts = :" + resp[2] );   
       returnTime = Long.parseLong(resp[2].trim());   
    }   
}