[网络协议]39.基于UDP协议的通信程序

1.什么是UDP，它的优缺点是什么？

UDP:用户数据报协议[无连接的协议]
缺点:不能保证数据的安全与可靠。
优点:消耗小，效率高

2.建立基于UDP的网络通讯程序需要使用的类和常用方法

基于UDP的网络通讯程序是不区分客户端和服务器。
java.net.DatagramPacket---该类表示数据报包。【打包被发送的数据/接收发来的数据】
构造方法:
DatagramPacket(byte[]?buf, int?length)?
构造一个 DatagramPacket用于接收长度的数据包length。【接收发来的数据的数据包】
DatagramPacket(byte[]?buf, int?length, InetAddress?address, int?port)?
构造用于发送长度的分组的数据报包 length指定主机上到指定的端口号。 【打包被发送的数据】

实例方法：
byte[]?? ?getData() 返回数据缓冲区。?
int?? ?getLength() 返回要发送的数据的长度或接收到的数据的长度。?
InetAddress?? ?getAddress() 返回该数据报发送或接收数据报的计算机的IP地址。
int?? ?getPort() 返回发送数据报的远程主机上的端口号，或从中接收数据报的端口号。

java.net.DatagramSocket 此类表示用于发送和接收数据报数据包的套接字。
构造方法
DatagramSocket() 构造数据报套接字并将其绑定到本地主机上的任何可用端口。【发包】?
DatagramSocket(int?port) 构造数据报套接字并将其绑定到本地主机上的指定端口。【收包】

实例方法
void?? ?send(DatagramPacket?p) 从此套接字发送数据报包。?
void?? ?receive(DatagramPacket?p) 从此套接字接收数据报包。?
void?? ?close() 关闭此数据报套接字。?

3.基于UDP协议的通信程序创建步骤:

发送方步骤:
1.将需要发送的数据通过
DatagramPacket(byte[]?buf, int?length, InetAddress?address, int?port) 构造方法打包好
2.通过DatagramSocket()的构造方法创建DatagramSocket对象。
3.DatagramSocket对象的send方法将打包好的数据报包，发送。
4.关闭DatagramSocket。

接收方步骤
1.通过DatagramSocket(int?port)创建接收数据的DatagramSocket对象。
2.通过DatagramPacket(byte[]?buf, int?length) 创建一个空的数据报包。
3.通过调用接收数据的DatagramSocket对象的receive方法接收数据报包到空的数据报包。
4.解析数据报包
5.关闭DatagramSocket

实例1:客户端向服务器发送数据，服务器接收客户端发送来的数据

package com.wangxing.udpdemo1;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPClient1 {
    public static void main(String[] args)throws Exception {
        BufferedReader  reader=null;
        String info=null;
        DatagramPacket  fasongbao=null;
        InetAddress address=null;
        int port=3000;
        DatagramSocket  sendSocket=null;

        reader=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("请输入需要发送的数据:");
        info=reader.readLine();
        // DatagramPacket(byte[]?buf, int?length, InetAddress?address, int?port)
        byte databyte[]=info.getBytes();
        address=InetAddress.getLocalHost();
        fasongbao=new DatagramPacket(databyte,databyte.length,address,port);
        //DatagramSocket()
        sendSocket=new DatagramSocket();
        //void	send(DatagramPacket?p) 从此套接字发送数据报包
        sendSocket.send(fasongbao);
        //void	close() 关闭此数据报套接字。
        sendSocket.close();
        reader.close();
    }
}


package com.wangxing.udpdemo1;

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPServer1 {
    public static void main(String[] args)throws Exception {
        DatagramSocket jieshouSocket=null;
        int port=3000;
        DatagramPacket  jieshoubao=null;
        String info=null;
        //DatagramSocket(int?port)
        jieshouSocket=new DatagramSocket(port);
        //DatagramPacket(byte[]?buf, int?length)
        byte  databyte[]=new byte[1024];
        jieshoubao=new DatagramPacket(databyte,databyte.length);
        jieshouSocket.receive(jieshoubao);
        //拆数据包
        //byte[]	getData()
        byte  shoudata[]=jieshoubao.getData();
        //int	getLength()
        int  length=jieshoubao.getLength();
        //InetAddress	getAddress()
        String fasongfangip=jieshoubao.getAddress().getHostAddress();
        //int	getPort()
        int fasongfangport=jieshoubao.getPort();
        info=new String(shoudata,0,length);
        System.out.println("接收来自"+fasongfangip+"从"+fasongfangport+"发出的数据是："+info);
        jieshouSocket.close();
    }
}

实例2:客户端向服务器持续发送数据，服务器持续接收客户端发送来的数据

package com.wangxing.udpdemo2;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPClient1 {
    public static void main(String[] args)throws Exception {
        BufferedReader  reader=null;
        String info=null;
        DatagramPacket  fasongbao=null;
        InetAddress address=null;
        int port=3000;
        DatagramSocket  sendSocket=null;
        boolean  flag=true;
        reader = new BufferedReader(new InputStreamReader(System.in));
        address = InetAddress.getLocalHost();
        //DatagramSocket()
        sendSocket = new DatagramSocket();
        while(flag) {
            System.out.println("请输入需要发送的数据:");
            info = reader.readLine();
            if(info.equals("bey")){
                flag=false;
                System.out.println("关闭退出");
            }
                // DatagramPacket(byte[]?buf, int?length, InetAddress?address, int?port)
                byte databyte[] = info.getBytes();
                fasongbao = new DatagramPacket(databyte, databyte.length, address, port);
                //void	send(DatagramPacket?p) 从此套接字发送数据报包
                sendSocket.send(fasongbao);

        }
        //void	close() 关闭此数据报套接字。
        sendSocket.close();
        reader.close();
    }
}


package com.wangxing.udpdemo2;

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPServer1 {
    public static void main(String[] args)throws Exception {
        DatagramSocket jieshouSocket=null;
        int port=3000;
        DatagramPacket  jieshoubao=null;
        String info=null;
        boolean  flag=true;
        //DatagramSocket(int?port)
        jieshouSocket = new DatagramSocket(port);
        //DatagramPacket(byte[]?buf, int?length)
        byte databyte[] = new byte[1024];
        jieshoubao = new DatagramPacket(databyte, databyte.length);
        while(flag) {
            jieshouSocket.receive(jieshoubao);
            //拆数据包
            //byte[]	getData()
            byte shoudata[] = jieshoubao.getData();
            //int	getLength()
            int length = jieshoubao.getLength();
            //InetAddress	getAddress()
            String fasongfangip = jieshoubao.getAddress().getHostAddress();
            //int	getPort()
            int fasongfangport = jieshoubao.getPort();
            info = new String(shoudata, 0, length);
            if(info.equals("bey")){
                flag=false;
                System.out.println("关闭退出");
            }
            System.out.println("接收来自" + fasongfangip + "从" + fasongfangport + "发出的数据是：" + info);
        }
        jieshouSocket.close();
    }
}

实例3:客户端向服务器持续发送并接收数据，服务器持续接收客户端发送并接收数据。

package com.wangxing.udpdemo3;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPclient {
    public static void main(String[] args)throws Exception {
        BufferedReader  bufferedReader=null;
        String info=null;
        DatagramPacket fasongbao=null;
        InetAddress  serveradsress=null;
        int serverport=3000;
        DatagramSocket  sendsocket=null;
        DatagramPacket jeishoubao=null;
        byte jieshoubyte[]=null;
        DatagramSocket  jieshousocket=null;
        int port=4000;
        String  msg=null;
        boolean  flag=true;

        bufferedReader=new BufferedReader(new InputStreamReader(System.in));
        serveradsress=InetAddress.getLocalHost();
        sendsocket=new DatagramSocket();
        jieshoubyte=new byte[1024];
        jeishoubao=new DatagramPacket(jieshoubyte,jieshoubyte.length);
        jieshousocket=new DatagramSocket(port);
        while (flag) {
            System.out.println("请输入需要发送的数据:");
            info = bufferedReader.readLine();
            byte fasongbyte[]=info.getBytes();
            fasongbao=new DatagramPacket(fasongbyte,fasongbyte.length,serveradsress,serverport);
            sendsocket.send(fasongbao);
            if(info.equals("886")){
                flag=false;
                System.out.println("退出程序");
            }else{
                //接收数据
                jieshousocket.receive(jeishoubao);
                //拆数据
                msg=new String(jeishoubao.getData(),0,jeishoubao.getLength());
                System.out.println("接收来自服务器的数据是："+msg);
            }
        }
        jieshousocket.close();
        sendsocket.close();
        bufferedReader.close();
    }
}


package com.wangxing.udpdemo3;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPserver {
    public static void main(String[] args) throws Exception{
        DatagramPacket jeishoubao=null;
        byte jieshoubyte[]=null;
        DatagramSocket jieshousocket=null;
        int port=3000;
        String  msg=null;
        DatagramPacket fasongbao=null;
        InetAddress clientadsress=null;
        int clientport=4000;
        DatagramSocket  sendsocket=null;
        boolean  flag=true;

        jieshoubyte=new byte[1024];
        jeishoubao=new DatagramPacket(jieshoubyte,jieshoubyte.length);
        jieshousocket=new DatagramSocket(port);
        System.out.println("服务器启动");
        clientadsress=InetAddress.getLocalHost();
        sendsocket=new DatagramSocket();
        while(flag){
            jieshousocket.receive(jeishoubao);
            msg=new String(jeishoubao.getData(),0,jeishoubao.getLength());
            System.out.println("接收到来自客户端的数据是:"+msg);
            if(msg.equals("886")){
                flag=false;
                System.out.println("退出程序");
            }else{
                msg="server-"+msg;
                byte sendbyte[]=msg.getBytes();
                fasongbao=new DatagramPacket(sendbyte,sendbyte.length,clientadsress,clientport);
                sendsocket.send(fasongbao);
            }
        }
        sendsocket.close();
        jieshousocket.close();
    }
}