ex4

src/Ex4/App.java

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+package Ex4;
+
+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));
+        client.sendMessage("DATE");
+		client.sendMessage("HOUR");
+		client.sendMessage("FULL");
+		client.sendMessage("CLOSE");
+
+        // stopping server
+        server.close();
+    }
+}

src/Ex4/Client.java

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+package Ex4;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+
+public class Client {
+
+	private final Socket socket;
+
+	/**
+	 * Create a new client
+	 * 
+	 * @param address server adress (needed
+	 * @throws IOException
+	 */
+	public Client(InetSocketAddress address) throws IOException {
+		this.socket = new Socket(address.getAddress(), address.getPort());
+		
+	}
+
+	public void sendMessage(String message) {
+		PrintWriter writer;
+		try {
+			writer = new PrintWriter(this.socket.getOutputStream(), true);
+			writer.println(message);
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+		readMessage();
+	}
+
+	private void readMessage() {
+		try {
+			BufferedReader reader = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
+			System.out.println("[Client] " + reader.readLine());
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+	}
+
+}

src/Ex4/Server.java

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+package Ex4;
+
+import java.io.BufferedOutputStream;
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.net.SocketException;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.GregorianCalendar;
+
+public class Server {
+
+	private final ServerSocket serverSocket;
+
+	public Server(int port) throws IOException {
+		this.serverSocket = new ServerSocket(port);
+		new Thread(this::listen).start();
+		System.out.println("Server running on port " + getPort());
+	}
+
+	public void close() {
+		try {
+			this.serverSocket.close();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+	}
+
+	public int getPort() {
+		return this.serverSocket.getLocalPort();
+	}
+
+	private void processConnexion(Socket socket) throws IOException {
+		new Thread(new Runnable() {
+			@Override
+			public void run() {
+				try {
+					readMessages(socket);
+				} catch (IOException e) {
+					e.printStackTrace();
+				}
+			}
+		}).start();
+	}
+
+	private void listen() {
+		try {
+			while (true) {
+				Socket connexion = this.serverSocket.accept();
+				processConnexion(connexion);
+			}
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+	}
+
+	private void readMessages(Socket socket) throws IOException {
+		BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
+		PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
+		boolean done = false;
+		while (!done) {
+			String message = reader.readLine();
+			Date date = Date.from(Instant.now());
+			Calendar now = GregorianCalendar.getInstance();
+			now.setTime(date);
+			System.out.println("[Server] Received " + message);
+			switch (message) {
+				case "DATE":
+					writer.println(LocalDate.now());
+					break;
+
+				case "HOUR":
+					writer.println(now.get(Calendar.HOUR_OF_DAY) + ":" + now.get(Calendar.MINUTE));
+					break;
+
+				case "FULL":
+					writer.println(Instant.now().toString());
+					break;
+
+				case "CLOSE":
+					System.out.println("[Server] Closing socket...");
+					socket.close();
+					done = true;
+					break;
+
+				default:
+					break;
+			}
+		}
+	}
+
+}