一．UDP网络编程

1.面向无连接的数据传输，不可靠的，但效率高（音频，视频等）.2.UDP一次发送的数据不能超过64kb.3.UDP编程所需要的类（1）DatagramSocket此类表示用来发送和接收数据报包的套接字（2）DatagramPacket此类表示数据报包方法：DatagramPacket(byte[] buf, int length, InetAddress address, int port)参数表示：buf - 包数据length - 包长度address - 目的地址port - 目的端口4.DatagramSocket常用方法（1）构造方法：public DatagramSocket(int port)（2）常用方法：#public void send(DatagramPacket p)#public void receive(DatagramPacket p)5.DatagramPacket常用方法（1）构造方法：public DatagramPacket(byte[] buf,int length)此构造方法用来接收数据（2）public DatagramPacket(byte[] buf, int length, InetAddress address, int port) 此构造方法用来组装将要发送的数据（3）public InetAddress getAddress():返回将要发送ign方的IP或者接收到的数据的IP（4）public byte[] getData():返回将要发送的数据缓冲区或已经接收到的数据缓冲区（5）public int getLength():返回要发送的数据长度或接收到的数据长度 6.基于TCP与UDP协议的网络编程（区别）：（1）基于TCP协议的Socket编程：#.通信双发需要建立连接；#.连接建立时双方存在主次之分（2）基于UDP协议的Socket编程:#.通信双发不需要建立连接；#.通信双方完全平等7.基于UDP协议的Socket编程（1）UDP Socket通信模型：例（UDP示例）：信息发送线程类：

package udp;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;//发送线程类public class SendRunnable implements Runnable{    private String destHost;    private int port;    private DatagramSocket ds;    public SendRunnable(String destHost, int port, DatagramSocket ds) {        this.destHost = destHost;        this.port = port;        this.ds = ds;    }    @Override    public void run() {        while(true){            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));            System.out.print(Thread.currentThread().getName()+":");            String say;            DatagramPacket dp=null;            try {                say=br.readLine();                dp=new DatagramPacket(say.getBytes(),say.getBytes().length ,InetAddress.getByName(destHost), port);                ds.send(dp);             } catch (IOException e) {                e.printStackTrace();            }        }    }}

信息接收线程类：

package udp;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;/*接收线程类 */public class ReceiveRunnable implements Runnable {    private DatagramSocket ds;    public ReceiveRunnable(DatagramSocket ds) {        this.ds = ds;    }    @Override    public void run() {        while (true) {            byte[] b = new byte[1024];            DatagramPacket dp = new DatagramPacket(b, b.length);            try {                ds.receive(dp);// 接收之前一直阻塞                String ip = dp.getAddress().getHostName();// 获取发送方的IP                int post = dp.getPort();// 获取发送方的端口号                System.out.println(ip + ":" + post + "说："                        + new String(dp.getData(), 0, dp.getLength()));            } catch (IOException e) {                e.printStackTrace();            }        }    }}

聊天端口一：

package udp;import java.net.DatagramSocket;import java.net.SocketException;class Chat1 {    public static void main(String[] args) throws SocketException {        DatagramSocket ds=new DatagramSocket(9999);        new Thread(new ReceiveRunnable(ds)).start();        new Thread(new SendRunnable("localhost", 8888, ds),"白雪公主").start();    }}

聊天端口二：

package udp;import java.net.DatagramSocket;import java.net.SocketException;public class Chat2 {    public static void main(String[] args) throws SocketException {        DatagramSocket ds=new DatagramSocket(8888);        new Thread(new ReceiveRunnable(ds)).start();        new Thread(new SendRunnable("localhost", 9999, ds),"青蛙王子").start();    }

}

运行结果

白雪公主:127.0.0.1:8888说：你好，公主你好，王子白雪公主:127.0.0.1:8888说：你在干什摸，公主我在和你聊天白雪公主:：青蛙王子:你好，公主青蛙王子:127.0.0.1:9999说：你好，王子你在干什摸，公主青蛙王子:127.0.0.1:9999说：我在和你聊天