added host input, recording and measurement of timestamps

VerteilteSysteme-Examples/src/verteiltesysteme/socket/timecounter/UDPTimeCounterClient.java

@@ -11,31 +11,44 @@ import java.util.Date;
 
 class UDPTimeCounterClient {
 	public static void main(String args[]) throws Exception {
-		String hostname = "192.168.73.158";
+		String hostname = "";
 		int udpPort = 36038;
 		BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
 		DatagramSocket clientSocket = new DatagramSocket();
-		InetAddress IPAddress = InetAddress.getByName(hostname);
 		byte[] sendData = new byte[1024];
 		byte[] receiveData = new byte[1024];
 		DateFormat df = new SimpleDateFormat("dd.MM.yyyy HH:mm:ss");
 				
+		System.out.println("Bitte geben Sie die Server-Adresse ein: ");
+		hostname = inFromUser.readLine();
+		InetAddress IPAddress = InetAddress.getByName(hostname);
 		System.out.println("Bitte geben Sie eine Zahl ein: ");
 		Long number = new Long(inFromUser.readLine());
 		sendData = number.toString().getBytes();
 
 		System.out.println(System.lineSeparator());
-		System.out.println("Zeit vor Versand = " + System.currentTimeMillis() + " " + df.format(new Date(System.currentTimeMillis())));
+		long timestampStart = System.currentTimeMillis();
+		System.out.println("Zeit vor Versand = " + timestampStart + " ms, " + df.format(new Date(timestampStart)));
 		DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, udpPort);
 		clientSocket.send(sendPacket);
-		System.out.println("Zeit nach Versand = " + System.currentTimeMillis() + " " + df.format(new Date(System.currentTimeMillis())));
+		long timestampSent = System.currentTimeMillis();
+		System.out.println("Zeit nach Versand = " + timestampSent + " ms, " + df.format(new Date(timestampSent)));
 		DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
+
 		clientSocket.receive(receivePacket);
-		System.out.println("Zeit nach Empfang = " + System.currentTimeMillis() + " " + df.format(new Date(System.currentTimeMillis())));
+
+		long timestampEnd = System.currentTimeMillis();
+		System.out.println("Zeit nach Empfang = " + timestampEnd + " ms, " + df.format(new Date(timestampEnd)));
+		long delay = timestampEnd - timestampStart;
+		System.out.println("Delay = " + delay + " ms");
 		System.out.println(System.lineSeparator());
 		
 		String result = new String(receivePacket.getData());
 		System.out.println("Ausgabe vom Server:" + System.lineSeparator() + result);
+		long timestampServer = new Long(result.split(" ")[2]).longValue();
+		float oneWayDelayEstimate = (timestampEnd - timestampSent) / 2;
+		float timestampSkew = timestampServer - timestampSent - oneWayDelayEstimate;
+		System.out.println("Zeitversatz zwischen Server und Client ca. = " + timestampSkew + " ms");
 		System.out.println(System.lineSeparator());
 		clientSocket.close();
 	}

VerteilteSysteme-Examples/src/verteiltesysteme/socket/timecounter/UDPTimeCounterServer.java

@@ -27,6 +27,7 @@ class UDPTimeCounterServer {
 			int clientSrcPort = receivePacket.getPort();
 
 			counter += number;
+			
 			sendData = (Long.toString(counter) + " Zeit: " + System.currentTimeMillis() + " " + df.format(new Date(System.currentTimeMillis()))).getBytes();
 			DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, clientSrcPort);
 			serverSocket.send(sendPacket);