From f5a11fc2de3eb2051eb95538cabb350523fe7fea Mon Sep 17 00:00:00 2001
From: Persson-dev <sim16.prib@gmail.com>
Date: Wed, 4 Feb 2026 09:24:56 +0100
Subject: [PATCH] ex2

---
 src/Ex1/Client.java |  2 --
 src/Ex2/App.java    | 10 ++++++
 src/Ex2/Client.java | 77 +++++++++++++++++++++++++++++++++++++++++++++
 src/Ex2/Server.java | 52 ++++++++++++++++++++++++++++++
 4 files changed, 139 insertions(+), 2 deletions(-)
 create mode 100644 src/Ex2/App.java
 create mode 100644 src/Ex2/Client.java
 create mode 100644 src/Ex2/Server.java

diff --git a/src/Ex1/Client.java b/src/Ex1/Client.java
index 188b34c..626455f 100644
--- a/src/Ex1/Client.java
+++ b/src/Ex1/Client.java
@@ -4,8 +4,6 @@ import java.io.IOException;
 import java.net.DatagramPacket;
 import java.net.DatagramSocket;
 import java.net.InetSocketAddress;
-import java.util.Random;
-import java.util.Scanner;
 
 public class Client {
 
diff --git a/src/Ex2/App.java b/src/Ex2/App.java
new file mode 100644
index 0000000..6e868ce
--- /dev/null
+++ b/src/Ex2/App.java
@@ -0,0 +1,10 @@
+package Ex2;
+
+import java.net.InetSocketAddress;
+
+public class App {
+    public static void main(String[] args) throws Exception {
+        Server server = new Server(6666);
+        Client client = new Client(new InetSocketAddress("localhost", 6666));
+    }
+}
diff --git a/src/Ex2/Client.java b/src/Ex2/Client.java
new file mode 100644
index 0000000..dc56796
--- /dev/null
+++ b/src/Ex2/Client.java
@@ -0,0 +1,77 @@
+package Ex2;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetSocketAddress;
+import java.sql.Timestamp;
+import java.time.Instant;
+import java.time.temporal.TemporalUnit;
+
+public class Client {
+
+	private final DatagramSocket socket;
+	private final InetSocketAddress address;
+
+	/**
+	 * Create a new client
+	 * 
+	 * @param address server adress (needed
+	 * @throws IOException
+	 */
+	public Client(InetSocketAddress address) throws IOException {
+		this.address = address;
+		this.socket = new DatagramSocket();
+		sendGreetings();
+		readMessage();
+		this.socket.close();
+	}
+
+	private void sendGreetings() throws IOException {
+		sendMessage(Instant.now().toString());
+	}
+
+	public void sendMessage(String message) throws IOException {
+		byte[] buffer = message.getBytes();
+		DatagramPacket packet = new DatagramPacket(buffer, buffer.length, this.address.getAddress(),
+				this.address.getPort());
+		this.socket.send(packet);
+	}
+
+	private void processMessage(DatagramPacket packet) {
+		String message = new String(packet.getData(), 0, packet.getLength());
+		long t2 = Instant.now().toEpochMilli();
+		System.out.println("[Client] Message recieved : " + message);
+		String[] times = message.split(" ");
+		long t1 = Instant.parse(times[0]).toEpochMilli();
+		long tPrime1 = Instant.parse(times[1]).toEpochMilli();
+		long tPrime2 = Instant.parse(times[2]).toEpochMilli();
+		var delta = (t2 - t1) - (tPrime2 - tPrime1);
+		var theta = (tPrime1 + tPrime2) / 2 - (t1 + t2) / 2;
+		var now = System.currentTimeMillis();
+		System.out.println("Delta : " + delta + "ms, Theta : " + theta + "ms");
+		System.out.println("Temps actuel : " + new Timestamp(now));
+		System.out.println("Temps corrigé: " + new Timestamp(now + theta));
+	}
+
+	private boolean readMessage() {
+		byte[] buffer = new byte[1024];
+		DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
+		try {
+			this.socket.receive(packet);
+			processMessage(packet);
+		} catch (IOException e) {
+			e.printStackTrace();
+			return false;
+		}
+		return true;
+	}
+
+	private void readMessages() {
+		while (true) {
+			if(!readMessage())
+				break;
+		}
+	}
+
+}
diff --git a/src/Ex2/Server.java b/src/Ex2/Server.java
new file mode 100644
index 0000000..5e38c3d
--- /dev/null
+++ b/src/Ex2/Server.java
@@ -0,0 +1,52 @@
+package Ex2;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.net.SocketException;
+import java.time.Instant;
+
+public class Server {
+
+	private final DatagramSocket socket;
+
+	public Server(int port) throws SocketException {
+		this.socket = new DatagramSocket(port);
+		new Thread(this::readMessages).start();
+	}
+
+	public int getPort() {
+		return this.socket.getLocalPort();
+	}
+
+	private void sendMessage(String message, InetAddress address, int port) throws IOException {
+		byte[] buffer = message.getBytes();
+		DatagramPacket packet = new DatagramPacket(buffer, buffer.length, address, port);
+		this.socket.send(packet);
+	}
+
+	private void processMessage(DatagramPacket packet) throws IOException {
+		Instant tPrime1 = Instant.now();
+		String message = new String(packet.getData(), 0, packet.getLength());
+		System.out.println("[Server] Message recieved : " + message);
+		Instant t1 = Instant.parse(message);
+		Instant tPrime2 = Instant.now();
+		sendMessage(t1.toString() + " " + tPrime1.toString() + " " + tPrime2.toString(), packet.getAddress(), packet.getPort());
+	}
+
+	private void readMessages() {
+		while (true) {
+			byte[] buffer = new byte[1024];
+			DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
+			try {
+				this.socket.receive(packet);
+				processMessage(packet);
+			} catch (IOException e) {
+				e.printStackTrace();
+				break;
+			}
+		}
+	}
+
+}