目录1、前提知识2、实现思路：
1、前提知识
需要知道简单的IO流操作，以及简单的UDP发送数据包的原理。
需要用到的类：DatagramSocket、DatagramPacket
UDP数据包基于DatagramSocket发送和接收，DatagramPacket用于封装数据包
看下案例：
客户端发送消息：
正常情况下从控制台读信息，封装到DatagramPacket之中，再由DatagramSocket的send方法发出
读取到bye的时候退出聊天
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(); }}
服务端接收消息：
DatagramSocket的receive方法接收客户端发送的消息，打印到控制台，如果信息是bye则退出聊天
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(); }}
试验：正常开启客户端和服务端后：
客户端发送消息：
服务端接收到信息即成功：
有了这个思路，我们只需要把发送和接收封装成发送类和接收类，使用多线程即可实现聊天了
2、实现思路：
创建UDP发送实现类TaskSend、UDP接收实现类TaskReceive，以及模拟多线程通信的通信类ChatThread1、ChatThread2
UDP发送实现类TaskSend：
public class TaskSend implements Runnable{ private String sendIP; //自己的服务端口 private int ownPort; private int sendPort; //读取控制台输入流 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 { } } //发送消息 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接收实现类TaskReceive：
public class TaskReceive implements Runnable{ private int ownPort; //发送信息的人 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(); }}
之后使用两个通信类开启多线程模拟一下：
模拟老师
public class ChatThread1 { public static void main(String[] args) { new Thread(new TaskSend("localhost",9999,10000)).start(); new Thread(new TaskReceive(9998,"老师")).start(); }}
模拟学生
public class ChatThread2 { public static void main(String[] args) { new Thread(new TaskReceive(9999,"学生")).start(); new Thread(new TaskSend("localhost",9998,10001)).start(); }}
实例：
学生
老师
到此简单的在线聊天功能就完成了，可以巩固一下之前学习的网络知识
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