import java.net.*;

public class EchoClient {

    public static void main(String[] args) {
	if (args.length!=2) {
	    System.out.println("java EchoClient <hostname> <port>");
	    System.exit(0);
	}
	int port=0;
	InetAddress server=null;
	try {
	    server = InetAddress.getByName(args[0]);
	    port=Integer.parseInt(args[1]);
	} catch (Exception ex) {
	    System.out.println("java EchoClient <hostname> <port>");
	    System.exit(0);
	}
	EchoClient client = new EchoClient(server, port);

    }

    public EchoClient(InetAddress server, int port) {
	
	try {
	    // client socket mit beliebigem freien UDP Port aufmachen
	    DatagramSocket sock = new DatagramSocket();

	    // neuen thread starten, der auf Antworten wartet
	    Receiver rec = new Receiver(sock);

	    byte[] data = new byte[1];
	    
	    for (byte i=0; i<10; i++) {
		data[0]=i;

		// request Paket zusammenbauen
		DatagramPacket pack = new DatagramPacket(data,
							 1,
							 server,
							 port);
		// und weg damit ...
		sock.send(pack);
		System.out.println("Sent ping request sequ  : "+i+" at "+System.currentTimeMillis());
		Thread.currentThread().sleep(1000);
	    }
	} catch (Exception ex) {
	    System.out.println("Encountered unexpected exception: "+ex);
	}
	System.exit(0);
    }
}

// Thread der auf Antworten wartet analog zum server Programm ...

class Receiver extends Thread {

    DatagramSocket sock;

    Receiver (DatagramSocket s) {
	sock = s;
	start();
    }

    public void run() {
	byte[] data = new byte[1];
	DatagramPacket reply = new DatagramPacket(data,1);

	try {
	    while (true) {
		sock.receive(reply);
		System.out.println("Received ping reply sequ: "+(reply.getData())[0]+" at "+System.currentTimeMillis());
	    }
	} catch (Exception ex) {
	    System.out.println("Encountered unexpected exception: "+ex);
	    System.exit(0);
	}
    }
}