网络编程

目的：数据交换、通信

1. 网络通信的要素

通信双方地址（IP+端口号）
网络通信协议

Java万物皆对象

2. IP地址

IP地址的类：InetAddress

唯一定位一台网络上的计算机
127.0.0.1 本机地址

package com.xiaozhang.lesson01;
import java.net.InetAddress;
//InetAddress类，无构造器，使用静态方法
import java.net.UnknownHostException;

//测试IP
public class TestInetAdress {
    public static void main(String[] args) {
        try {
            //查询本机地址
            InetAddress inetAdress1 = InetAddress.getByName("127.0.0.1");
            InetAddress inetAdress2 = InetAddress.getByName("localhost");
            InetAddress inetAdress3 = InetAddress.getLocalHost();
            //根据网站域名查询网站IP地址
            InetAddress inetAdress4 = InetAddress.getByName("www.baidu.com");
            //常用方法
            System.out.println(inetAdress4.getCanonicalHostName());//规范ip
            System.out.println(inetAdress4.getHostAddress());//ip
            System.out.println(inetAdress4.getHostName());//域名
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

3. 端口

端口的类：InetScoketAddress

端口对应进程
TCP / UDP下各0~65535
公有端口：0~1023
程序注册端口：1024~49151
动态、私有：49152~65535

//查询所有的端口
netstat -ano
//查询具体的端口
netstat -ano|findstr "8080"
//查询指定端口的进程
tasklist|findstr "8080"

package com.xiaozhang.lesson01;
import java.net.InetSocketAddress;
public class TestInetSocketAddress {

    public static void main(String[] args) {
        InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1",8080);
        System.out.println(inetSocketAddress.toString());
        System.out.println(inetSocketAddress.getAddress());
        System.out.println(inetSocketAddress.getHostName());
        System.out.println(inetSocketAddress.getPort());
    }
}

4. 网络通信协议

TCP/IP协议簇：实际上是一组协议

TCP：用户传输协议
UDP：用户数据报协议
IP：网络互联协议

5. TCP

客户端

连接服务器Socket
发送消息

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

//客户端
public class TcpClientDemo01 {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        try {
            //1.获取服务器地址，端口号
            InetAddress serverIp = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            //2.创建一个socket连接
            socket = new Socket(serverIp,port);
            //3.发送消息 IO流
            os = socket.getOutputStream();
            os.write("你好!".getBytes());

        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            //关闭连接
            if (os!=null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket!=null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

服务器

建立服务的端口ServerSocket
等待用户的连接 accept
接受用户的消息

package com.xiaozhang.lesson02;

import jdk.nashorn.internal.objects.annotations.Where;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

//服务端
public class TcpServerDemo01 {
    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;

        try {
            //1.创建服务器地址
            serverSocket = new ServerSocket(9999);

            while (true){
                //2.等待客户端链接过来
                socket = serverSocket.accept();
                //3.读取客户端的消息
                is = socket.getInputStream();

                //管道流
                baos = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024];
                int len;
                while((len=is.read(buffer))!=-1){
                    baos.write(buffer,0,len);
                }
                System.out.println(baos.toString());
            }


        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                /*
                严谨写法:
                if(baos!=null){
                    baos.close();
                }
                ......
                 */
                //关闭资源
                baos.close();
                is.close();
                socket.close();
                serverSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

5.1 文件上传

客户端

package com.xiaozhang.lesson02;

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;

public class TcpClientDemo02 {
    public static void main(String[] args) throws Exception {
        //1.创建一个Socket连接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"),9000);
        //2.创建一个输出流
        OutputStream os = socket.getOutputStream();
        //3.读取文件
        FileInputStream fis = new FileInputStream(new File("1111.jpg"));
        //4.写出文件
        byte[] buffer = new byte[1024];
        int len;
        while ((len=fis.read(buffer))!=-1){
            os.write(buffer,0,len);
        }
        //通知服务器发送完毕
        socket.shutdownOutput();

        //确定服务器接收完毕,才能够断开连接
        InputStream inputStream = socket.getInputStream();

        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        byte[] buffer2 = new byte[1024];
        int len2;
        while((len2=inputStream.read(buffer2))!=-1){
            baos.write(buffer2,0,len2);
        }
        System.out.println(baos.toString());

        //5.关闭资源
        baos.close();
        inputStream.close();
        fis.close();
        os.close();
        socket.close();
    }
}

服务器

package com.xiaozhang.lesson02;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class TcpServerDemo02 {
    public static void main(String[] args) throws Exception {
        //1.创建服务
        ServerSocket serverSocket = new ServerSocket(9000);
        //2.监听客户端的连接
        Socket socket = serverSocket.accept();//阻塞式监听,会一直等待客户端连接
        //3.获取输入流
        InputStream is = socket.getInputStream();
        //4.文件输出
        FileOutputStream fos = new FileOutputStream(new File("receive1.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = is.read(buffer))!=-1){
            fos.write(buffer,0,len);
        }
        //通知客户端接收完毕
        OutputStream os = socket.getOutputStream();
        os.write("接收完毕".getBytes());

        //关闭资源
        fos.close();
        is.close();
        socket.close();
        serverSocket.close();
    }
}

6. UDP

6.1 发送消息

发送端

package com.xiaozhang.lesson03;

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

//UDP无连接
//发送端
public class UdpClientDemo01 {
    public static void main(String[] args) throws Exception {
        //1.建立Socket
        DatagramSocket socket = new DatagramSocket();
        //2.建个包
        String msg = "你好,服务器!";
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;
        //(数据,数据起始,数据长度,发送给谁,端口号)
        DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);

        //3.发送包
        socket.send(packet);

        //4.关闭socket
        socket.close();
    }  
}

接收端

package com.xiaozhang.lesson03;

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

//接收端
public class UdpServerDemo01 {
    public static void main(String[] args) throws Exception{
        //开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

        socket.receive(packet);//阻塞接收
        System.out.println(new String(packet.getData(),0,packet.getLength()));
        //关闭socket
        socket.close();
    }
}

6.2 单向聊天

发送端

package com.xiaozhang.chat;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketException;

public class UdpSenderDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(8888);
        //读取控制台的输入
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        while (true){
            String data = reader.readLine();
            byte[] datas = data.getBytes();
            DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress("localhost",6666));
            socket.send(packet);
            if (data.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

接收端

package com.xiaozhang.chat;

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

public class UdpReceiveDemo01 {
    public static void main(String[] args) throws Exception{
        DatagramSocket socket = new DatagramSocket(6666);
        while (true){
            //准备接受的包
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container,0,container.length);
            socket.receive(packet);

            //断开连接
            byte[] data = packet.getData();
            String receivedata = new String(data, 0, data.length);

            System.out.println(receivedata);
            if (receivedata.equals("bye")){
                break;
            }
        }
        socket.close();
    }
}

6.3 双向聊天

学生,老师
在这里插入图片描述

工具类

package com.xiaozhang.chat;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class TalkSend implements Runnable{
    DatagramSocket socket = null;
    BufferedReader reader = null;
    private  int fromPort;
    private String toIP;
    private int toPort;


    public TalkSend(int fromPort, String toIP, int toPort) {
        this.fromPort = fromPort;
        this.toIP = toIP;
        this.toPort = toPort;

        try {
            socket = new DatagramSocket(fromPort);
            reader = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        while (true){
            try {
                String data = reader.readLine();
                byte[] datas = data.getBytes();
                DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress(this.toIP,this.toPort));

                socket.send(packet);
                if (data.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

package com.xiaozhang.chat;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class TalkReceive implements Runnable{
    DatagramSocket socket = null;
    private int port;
    private String msgFrom;

    public TalkReceive(int port,String msgFrom) {
        this.port = port;
        this.msgFrom = msgFrom;
        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
        while (true){
            //准备接受的包
            try {
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container,0,container.length);
                socket.receive(packet);

                //断开连接
                byte[] data = packet.getData();
                String receivedata = new String(data, 0, data.length);

                System.out.println(msgFrom+":"+receivedata);
                if (receivedata.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

7. URL

在这里插入图片描述

7.1 URL下载

package com.xiaozhang.lesson03;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class URLDown {
    public static void main(String[] args) throws Exception {
        //下载地址
        URL url = new URL("https://m801.music.126.net/20221214224441/ec1f536fb497eb2f6099a70434c1e5fd/jdyyaac/5252/0e5a/5153/e8095592ba909dd03ca4f9b6b8889840.m4a");
        //连接到资源
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("download.m4a");
        byte[] buffer = new byte[1024];
        int len;
        while ((len=inputStream.read(buffer))!=-1){
            fos.write(buffer,0,len);//写出数据
        }
        fos.close();
        inputStream.close();
        urlConnection.disconnect();
    }
}