update:demo8

com/study/demo8/TCPClient.java

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+package com.study.demo8;
+
+import java.io.PrintWriter;
+import java.net.Socket;
+
+public class TCPClient {
+    public static void main(String[] args) {
+        try {
+            Socket socket = new Socket("localhost", 8888);
+            System.out.println("Connected to server.");
+
+            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
+            out.println("Hello Server");
+            System.out.println("Sent message to server.");
+
+            out.close();
+            socket.close();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

com/study/demo8/TCPServer.java

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+package com.study.demo8;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+public class TCPServer {
+    public static void main(String[] args) {
+        try {
+            ServerSocket serverSocket = new ServerSocket(8888);
+            System.out.println("Server started, waiting for client connection...");
+
+            Socket clientSocket = serverSocket.accept();
+            System.out.println("Client connected: " + clientSocket.getInetAddress().getHostAddress());
+
+            BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+            String message = in.readLine();
+            System.out.println("Received from client: " + message);
+
+            in.close();
+            clientSocket.close();
+            serverSocket.close();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

com/study/demo8/UDPReceiver.java

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+package com.study.demo8;
+
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+
+public class UDPReceiver {
+    public static void main(String[] args) {
+        try {
+            DatagramSocket socket = new DatagramSocket(9999);
+            System.out.println("Receiver started, waiting for data...");
+
+            byte[] buffer = new byte[1024];
+            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
+
+            socket.receive(packet);
+
+            String message = new String(packet.getData(), 0, packet.getLength());
+            System.out.println("Received from sender: " + message);
+
+            socket.close();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

com/study/demo8/UDPSender.java

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+package com.study.demo8;
+
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+
+public class UDPSender {
+    public static void main(String[] args) {
+        try {
+            DatagramSocket socket = new DatagramSocket();
+
+            String message = "Hello UDP";
+            byte[] data = message.getBytes();
+
+            InetAddress address = InetAddress.getByName("localhost");
+            DatagramPacket packet = new DatagramPacket(data, data.length, address, 9999);
+
+            socket.send(packet);
+            System.out.println("Sent message to receiver.");
+
+            socket.close();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}