廖雪峰Java13网络编程-1Socket编程-5UDP编程

1. UDP编程：

不需要建立连接
可以直接发送和接收数据

1.1 客户端

    DatagramSocket sock = new DatagramSocket(){}

    sock.connect(addr,9090);//并不建立连接

    //接收

    byte[] data=...;

    DatagramPacket packet = new DatagramPacket(data, data.length);

    sock.send(packet);

    //发送

    byte[] buffer = new byte[1024];

    DatagramPacket resp = new DatagramPacket(buffer, buffer.length);

    sock.receive(resp);

    //接收和发送都是通过DatagramPacket实现的

1.2 服务端：

    DatagramSocket ds = new DatagramSocket(9090);

    for( ; ; ){

        //接收

        byte[] buffer = new buffer[1024];

        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

        ds.receive(packet);

        //发送

        byte[] data = ...;

        packet.setData(data);

        ds.send(packet);

    }

1.3 实例

TCPClient.java

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.nio.charset.StandardCharsets;

public class UDPClient {

    public static void main(String[] args) throws Exception{

        InetAddress addr = InetAddress.getLoopbackAddress();

        try(DatagramSocket sock = new DatagramSocket()){

            sock.connect(addr,9090);

            byte[] data = "time".getBytes(StandardCharsets.UTF_8);

            DatagramPacket packet = new DatagramPacket(data,data.length);

            sock.send(packet);

            System.out.println("Data was sent");

            Thread.sleep(1000);

            byte[] buffer = new byte[1024];

            DatagramPacket resp = new DatagramPacket(buffer,buffer.length);

            sock.receive(resp);

            byte[] respData = resp.getData();

            String respText = new String(respData,0,resp.getLength());

            System.out.println("Response:"+respText);

        }

    }

}

TCPServer.java

package com.crazy;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.nio.charset.StandardCharsets;

import java.time.LocalDateTime;

public class UDPServer {

    public LocalDateTime currentTime(){

        return LocalDateTime.now();

    }

    public static void main(String[] args) throws Exception{

        DatagramSocket ds = new DatagramSocket(9090);

        System.out.println("UDP server ready");

        for(;;){

            byte[] buffer = new byte[1024];

            DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);

            ds.receive(packet);

            byte[] data = packet.getData();

            String s = new String(data, StandardCharsets.UTF_8);

            System.out.println("Pack received from : "+packet.getSocketAddress());

            String resp = LocalDateTime.now().toString();

            packet.setData(resp.getBytes(StandardCharsets.UTF_8));

            ds.send(packet);

        }

    }

}

先运行server

再运行client

2. 总结：

UDP编程模型：

客户端使用DatagramSocket.connect()指定远程地址和端口
服务器端用DatagramSocket(port)监听端口
双方通过receive/send读写数据
没有IO流接口

巴特西

廖雪峰Java13网络编程-1Socket编程-5UDP编程

1. UDP编程：

1.1 客户端

1.2 服务端：

1.3 实例

2. 总结：

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