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网络通信的要素

网络通信的要素

1. IP地址

InetAddress

唯一定位一台网络上的计算机
127.0.0.1：本机 localhost
IP地址的分类
- IPV4/IPV 6
  - IPV4：127.0.0.1 4个字节组成，0-255，42亿个；30亿都在北美，亚洲4亿
  - IPV6：128位。8个无符号整数（十六进制，abcde）
```
2001:0bb2:aaaa:0015:0000:0000:1aaa:1312
```
- 公网（互联网）-私网（局域网）
- 192.168.XX.XX 专门给组织内部使用的
- ABCD类地址
域名：解决记忆IP问题

2. Java中的InetAddress包

package com.wang.lesson01;

import java.net.InetAddress;
import java.net.UnknownHostException;

/**
 * @author wang
 * @creatTime 2020/8/7
 */
//测试IP
public class Test01 {
    public static void main(String[] args) {
        //快捷键 clt+alt+t
        try {
            //查询本机地址
            InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
            System.out.println(inetAddress1);
            InetAddress inetAddress3 = InetAddress.getByName("localhost");
            System.out.println(inetAddress3);
            InetAddress inetAddress4 = InetAddress.getLocalHost();
            System.out.println(inetAddress4);

            //查询网站IP地址
            InetAddress inetAddress2 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress2);

            //常用方法
            //System.out.println(inetAddress2.getAddress());
            System.out.println(inetAddress2.getCanonicalHostName());    //规范的名字
            System.out.println(inetAddress2.getHostAddress());          //ip
            System.out.println(inetAddress2.getHostName());             //域名，或者本机的名字

        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

3. 端口

端口表示计算机上的一个程序的进程

不同的进程有不同的端口号！用来区分软件！
被规定为0~65535
TCP，UDP：单个协议下，端口号不能冲突

端口分类

共有端口0~1023
- HTTP：80
- HTTPS：443
- FTP：21
- Telent：23
程序注册端口：1024~49151，分配给用户或者程序
- Tomcat：8080
- MySQL：3306
- Orale：1521
动态、私有：49152~65535

netstat -ano	#查看所有的端口
netstat -ano|findstr "5900"	#查看指定的端口
tasklist|findstr "8696"	#查看指定端口的进程
Ctrl + Shift + Esc	#打开任务管理器

package com.wang.lesson01;

import java.net.InetSocketAddress;

/**
 * @author wang
 * @creatTime 2020/8/7
 */
public class TestIntSocketAddress {
    public static void main(String[] args) {

        InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1", 8080);
        System.out.println(inetSocketAddress.toString());
        InetSocketAddress inetSocketAddress2 = new InetSocketAddress("localhost", 8080);
        System.out.println(inetSocketAddress2.toString());

        System.out.println(inetSocketAddress.getAddress());
        System.out.println(inetSocketAddress.getHostName());    //地址
        System.out.println(inetSocketAddress.getPort());        //端口
    }
}

4. 通信协议

协议：约定

网络通信协议：速率，传输码率，代码结构，传输控制

问题：复杂

解决方法：大事化小---->分层

TCP/IP协议簇：实际上是一种协议

重要

TCP：用户传输协议
UDP：用户数据报协议

出名的协议

TCP
IP：网络互连协议

TCP UDP对比

TCP：打电话

连接，稳定
三次握手，四次挥手
客户端，服务端
传输完成，释放连接，效率低

UDP：发短信

不连接，不稳定
客户端，服务端：没有明确的界限
不管有没有准备好，都可以发给你
类比：导弹
DDOS：饱和攻击

5. TCP

1. 客户端

连接服务器Socket
发送消息

package com.wang.lesson02;

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

/**
 * @author wang
 * @creatTime 2020/8/7
 */
//客户端
public class TCPClientDemo01 {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        try {
            //1.要知道服务器的地址
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            //2. 端口号
            int port = 9999;
            //3. 创建一个socket连接
            socket = new Socket(serverIP, port);
            //4. 发送消息IO流
            os = socket.getOutputStream();
            os.write("这是一行字".getBytes());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (socket != null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (os != null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

2. 服务器

建立服务端的端口
等待用户的连接accept()，返回客户的socket
接收用户的消息

package com.wang.lesson02;

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

/**
 * @author wang
 * @creatTime 2020/8/7
 */
//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. 我得有一个地址
            serverSocket = new ServerSocket(9999);
            //2. 等待客户端连接过来
            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 {
            //关闭资源
            if (baos != null){
                try {
                    baos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (is != null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (socket != null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            if (serverSocket != null){
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }
}

3. 文件上传

服务器端

package com.wang.lesson02;

import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Paths;

/**
 * @author wang
 * @creatTime 2020/8/7
 */
public class TCPServerDemo02 {
    public static void main(String[] args) throws Exception{
        //1.创建服务
        ServerSocket serverSocket = new ServerSocket(9999);
        //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，由于同名的文件存在时会抛出异常，因此先删除同名文件
        try{
            Files.delete(Paths.get("pic_receive.jpg"));
            Files.copy(is, Paths.get("pic_receive.jpg"));
        } catch (NoSuchFileException e) {
            //如果同名文件不存在，则在NoSuchFileException中直接复制
            Files.copy(is, Paths.get("pic_receive.jpg"));
        }

        //通知客户端我接收完毕了
        OutputStream os = socket.getOutputStream();
        os.write("我接收完毕了，你可以断开了".getBytes());

        is.close();
        socket.close();
        serverSocket.close();
    }
}

客户端

package com.wang.lesson02;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * @author wang
 * @creatTime 2020/8/7
 */
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("localhost"), 9999);
        //2. 创建一个输出流
        OutputStream os = socket.getOutputStream();

        //文件流 Files用copy写到输入输出流，用readAllXXX读进来
        //3. 读取文件
        Path filePath = Paths.get("pic.jpg");

        //4. 写出文件
        Files.copy(filePath, os);

        //通知服务器，我已经结束了
        socket.shutdownOutput();    //我已经传输完了

        //确定服务器接收完毕，才能断开连接
        InputStream inputStream = socket.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        byte[] buffer = new byte[1024];
        int len;
        while ((len = inputStream.read(buffer)) != -1){
            baos.write(buffer,0,len);
        }

        System.out.println(baos.toString());

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

6. Tomcat

服务端

自定义 S
Tomcat S：Java后台开发

客户端

自定义 C
浏览器 B

7. UDP

发短信：不用连接，需要知道对方的地址！

1. UDP实现发送消息

package com.wang.lesson03;

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

/**
 * @author wang
 * @creatTime 2020/8/10
 */

//不需要连接服务器
public class UDPClientDemo01 {
    public static void main(String[] args) throws Exception {
        //1.建立一个socket
        DatagramSocket socket = new DatagramSocket();

        //2.建个包
        String msg = "Hello, Server!";

        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;

        //数据，数据的长度起始，要发送给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);

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

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

UDP实现接收消息

package com.wang.lesson03;

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

/**
 * @author wang
 * @creatTime 2020/8/10
 */
//还要等待客户端的连接
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

        //关闭连接
        socket.close();

        //public String(byte[] bytes,int index,int length) 把字节数组的一部分转成字符串
        System.out.println(new String(packet.getData(), 0, packet.getData().length));
    }
}

2. 咨询

循环发送消息

package com.wang.chat;

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

/**
 * @author wang
 * @creatTime 2020/8/10
 */
public class UDPSenderDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(8888);

        //准备数据：控制台读取System.in
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        while (true) {
            String data = reader.readLine();
            byte[] dataBytes = data.getBytes();

            DatagramPacket packet = new DatagramPacket(dataBytes, 0, dataBytes.length, new InetSocketAddress("localhost", 6666));

            socket.send(packet);

            if (data.equals("bye"))
                break;
        }

        socket.close();

    }
}

循环接收消息

package com.wang.chat;

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

/**
 * @author wang
 * @creatTime 2020/8/10
 */
public class UDPReceiveDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(6666);

        while (true) {
            //准备接收包裹
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container, 0, container.length);

            socket.receive(packet); //阻塞式接收包裹

            //当接收到"bye"，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();
    }
}

3. 在线咨询

两个人都可以是发送方，也都可以是接收方：使用多线程

循环发送消息

package com.wang.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;

/**
 * @author wang
 * @creatTime 2020/8/10
 */
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() {

        //准备数据：控制台读取System.in
        while (true) {
            try {
                String data = reader.readLine();
                byte[] dataBytes = data.getBytes();

                DatagramPacket packet = new DatagramPacket(dataBytes, 0, dataBytes.length, new InetSocketAddress(this.toIP, this.toPort));

                socket.send(packet);

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

        socket.close();

    }
}

循环接收消息

package com.wang.chat;

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

/**
 * @author wang
 * @creatTime 2020/8/10
 */
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() {
        try {
            while (true) {
                //准备接收包裹
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);

                socket.receive(packet); //阻塞式接收包裹

                //当接收到"bye"，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();
    }
}

老师端

package com.wang.chat;

/**
 * @author wang
 * @creatTime 2020/8/10
 */
public class TalkTeacher {
    public static void main(String[] args) {
        //开启两个线程
        new Thread(new TalkSend(5555, "localhost", 8888)).start();
        new Thread(new TalkReceive(9999, "学生")).start();
    }
}

学生端

package com.wang.chat;

/**
 * @author wang
 * @creatTime 2020/8/10
 */
public class TalkStudent {
    public static void main(String[] args) {
        //开启两个线程
        new Thread(new TalkSend(7777, "localhost", 9999)).start();
        new Thread(new TalkReceive(8888, "老师")).start();
    }
}

8. URL

统一资源定位符：定位互联网上的某一个资源

DNS域名解析：www.baidu.com ===> XXX.XX.XX.X

组成：

协议://ip地址:端口/项目名/资源

可以少但是不能多

package com.wang.lesson04;

import java.net.MalformedURLException;
import java.net.URL;

/**
 * @author wang
 * @creatTime 2020/8/10
 */
public class URLDemo01 {
    public static void main(String[] args) throws MalformedURLException {
        URL url = new URL("http://localhost:8080/helloworld/index.jsp?username=wang&password=123");
        System.out.println(url.getProtocol());      //协议
        System.out.println(url.getHost());          //主机ip
        System.out.println(url.getPort());          //端口
        System.out.println(url.getPath());          //文件
        System.out.println(url.getFile());          //全路径
        System.out.println(url.getQuery());         //参数
    }
}

利用URL下载文件

package com.wang.lesson04;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * @author wang
 * @creatTime 2020/8/10
 */
public class URLDown {
    public static void main(String[] args) throws Exception {
        //1.下载地址
        URL url = new URL("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1597050462137&di=e81d42b6c04eeff13b8011bdcdb7b5e7&imgtype=0&src=http%3A%2F%2Ft8.baidu.com%2Fit%2Fu%3D1484500186%2C1503043093%26fm%3D79%26app%3D86%26f%3DJPEG%3Fw%3D1280%26h%3D853");

        //2.连接到这个资源 用Http
        HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();

        InputStream inputStream = urlConnection.getInputStream();

        //利用Path和Files简化文件的IO
        String filePath = "download_pic.jpg";
        Path path = Paths.get(filePath);
        //考虑到可能存在同名文件，先删除同名文件，再copy
        try {
            Files.delete(path);
            Files.copy(inputStream, path);
        } catch (NoSuchFileException e) {
            //不存在同名文件，会抛出NoSuchFileException，此时直接copy
            Files.copy(inputStream, path);
        }

        inputStream.close();
    }
}

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原文地址：https://www.cnblogs.com/wang-sky/p/13469832.html