需要知道簡單的IO流操作，以及簡單的UDP發(fā)送數(shù)據(jù)包的原理。

需要用到的類：DatagramSocket、DatagramPacket

UDP數(shù)據(jù)包基于DatagramSocket發(fā)送和接收，DatagramPacket用于封裝數(shù)據(jù)包

看下案例：

客戶端發(fā)送消息：

正常情況下從控制臺讀信息，封裝到DatagramPacket之中，再由DatagramSocket的send方法發(fā)出

讀取到bye的時候退出聊天

public class UdpOnlineClient { public static void main(String[] args) throws IOException {DatagramSocket socket = new DatagramSocket(10000);BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));while (true) { String data = bufferedReader.readLine(); byte[] datas = data.getBytes(); DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress('localhost', 9999)); socket.send(packet); if (data.equals('bye')){break; }}socket.close(); }}

服務(wù)端接收消息：

DatagramSocket的receive方法接收客戶端發(fā)送的消息，打印到控制臺，如果信息是bye則退出聊天

public class UdpOnlineServer { public static void main(String[] args) throws IOException {DatagramSocket socket = new DatagramSocket(9999);while (true){ byte[] buffer = new byte[1024]; DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length); socket.receive(packet); String msg = new String(packet.getData(), 0, packet.getLength()); System.out.println(msg); if(msg.equals('bye')){break; }}socket.close(); }}

試驗：正常開啟客戶端和服務(wù)端后：

客戶端發(fā)送消息：

服務(wù)端接收到信息即成功：

有了這個思路，我們只需要把發(fā)送和接收封裝成發(fā)送類和接收類，使用多線程即可實現(xiàn)聊天了

創(chuàng)建UDP發(fā)送實現(xiàn)類TaskSend、UDP接收實現(xiàn)類TaskReceive，以及模擬多線程通信的通信類ChatThread1、ChatThread2

UDP發(fā)送實現(xiàn)類TaskSend：

public class TaskSend implements Runnable{ private String sendIP; //自己的服務(wù)端口 private int ownPort; private int sendPort; //讀取控制臺輸入流 private BufferedReader bufferedReader; private DatagramSocket socket; public TaskSend(String sendIP, int ownPort, int sendPort) {this.sendIP = sendIP;this.sendPort = sendPort;try { socket = new DatagramSocket(ownPort); bufferedReader = new BufferedReader(new InputStreamReader(System.in));} catch (SocketException e) { e.printStackTrace();} finally {} } //發(fā)送消息 public void run() {while (true) { try {String data = bufferedReader.readLine();//打印自己的消息System.out.println('我：'+data);byte[] datas = data.getBytes();DatagramPacket packet = new DatagramPacket(datas, 0, datas.length,new InetSocketAddress(sendIP,sendPort));socket.send(packet);if (data.equals('bye')) { break;} } catch (IOException e) {e.printStackTrace(); } finally { }}socket.close(); }}

UDP接收實現(xiàn)類TaskReceive：

public class TaskReceive implements Runnable{ private int ownPort; //發(fā)送信息的人 private String msgOwner; private DatagramSocket socket; public TaskReceive(int ownPort, String msgOwner) {this.msgOwner = msgOwner;try { socket = new DatagramSocket(ownPort);} catch (SocketException e) { e.printStackTrace();} finally {} } //接收消息 public void run() {while (true) { try {byte[] buffer = new byte[1024];DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);socket.receive(packet);String msg = new String(packet.getData(), 0, packet.getLength());System.out.println(msgOwner+'：'+msg);if (msg.equals('bye')) { break;} } catch (IOException e) {e.printStackTrace(); } finally { }}socket.close(); }}

之后使用兩個通信類開啟多線程模擬一下：

模擬老師

public class ChatThread1 { public static void main(String[] args) {new Thread(new TaskSend('localhost',9999,10000)).start();new Thread(new TaskReceive(9998,'老師')).start(); }}

模擬學(xué)生

public class ChatThread2 { public static void main(String[] args) {new Thread(new TaskReceive(9999,'學(xué)生')).start();new Thread(new TaskSend('localhost',9998,10001)).start(); }}

實例：

學(xué)生

老師

到此簡單的在線聊天功能就完成了，可以鞏固一下之前學(xué)習(xí)的網(wǎng)絡(luò)知識

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