网络编程之UDP

TCP(面向链接) 在正式收发数据前,必须和对方建立可靠的链接
特点:安全(面向链接,保证对象一定能收到数据),传输数据大小无限制
缺点:效率低(因为有三次握手)

UDP和TCP一样是面向无连接的传输层协议,提供面向事务的简单不可靠信息传送服务
特点:无连接,安全,可靠性不高,效率高
发送方->接受方
1.创建DatagramSocket
2.准备要发送的数据
3.将发送的数据放到包裹里面
4.通过DatagramSocket将包裹发送出去
5.关闭Socket
发送方

1.不需要地址和端口号
DatagramSocket socket = new DatagramSocket();
String str = "好开心啊";
DatagramPack pack = new DatagramPacket(str.getBytes(),str.length,127.0.0.1,2333)
Socket.send(packet);

接收方

DatagramSocket socket  = new DatagramSocket(2333);
byte[] buf = new byte[1024];
DatagramPacket packet = new DatagramPacket(buf,length);
//阻塞程序向下进行
socket.receve(packet);
String str = new String(packet.getData(),0,pack.length);
System.out.println(str);

利用udp实现互相聊天

服务端

package com.qf.demo3;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InterfaceAddress;
import java.net.SocketException;
import java.util.Scanner;

public class Recive {

    public static void main(String[] args) {
        // 1 接收方的socket需要端口号
        DatagramSocket socket = null;
        try {
            socket = new DatagramSocket(5577);
            Scanner in = new Scanner(System.in);
            while (true) {
                // 接收
                byte[] buf = new byte[1024];
                DatagramPacket p = new DatagramPacket(buf, buf.length);
                socket.receive(p);
                String string = new String(p.getData(), 0, p.getLength());
                System.out.println("发送方发送的" + string + " " + p.getAddress().getHostAddress());
                // 回复数据
                System.out.println("包裹端口:"+p.getPort());
                System.out.println("请输入回复内容:");
                String string2 = in.next();
                
                DatagramPacket packet = new DatagramPacket(string2.getBytes(), string2.getBytes().length,
                     InetAddress.getLocalHost(), p.getPort());
                
                socket.send(packet);
            }
        } catch (SocketException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            if (socket != null) {
                socket.close();
            }
        }

    }
}

客户端

package com.qf.demo3;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Scanner;

/**
 * 1 发送方: socket 没有参数的 接收方 : socket 是有端口号
 * 2 send 的 packet 是带有 byte lenth InetAddress port receive的 packet 是带有 byte
 * lenth
 * 作业: 实现循环的发送和接收 数据由控制台输入
 */
public class Send {

    public static void main(String[] args) {

        // 1 发送方的快递点不需要参数
        DatagramSocket socket = null;
        Scanner in = new Scanner(System.in); 
        try {
            socket = new DatagramSocket();
            while (true) {
                // 2
                System.out.println("请输入内容:");
                String string = in.next();
                // 3 将数据放到包裹里面
                DatagramPacket packet = new DatagramPacket(string.getBytes(), string.getBytes().length,
                        InetAddress.getLocalHost(), 5577);
                // 4 发送
                socket.send(packet);

                // 接收 接收端的 回复
                byte[] buf = new byte[1024 * 63];
                DatagramPacket p = new DatagramPacket(buf, buf.length);
                socket.receive(p);

                String string2 = new String(p.getData(), 0, p.getLength());
                System.out.println("接收方回复" + string2);
            }
        } catch (SocketException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            if (socket != null) {
                socket.close();
            }
        }
    }
}