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java网络编程【b站狂神课程笔记】

1.1 概述

类似于平信信件

其中涉及计算机网络基本概念，网络编程的目的就是传播交流信息、数据交换、通信；达到的效果是需要如何准确定位到网络上的一台主机（IP、端口、资源），对主机进行数据传输

与JAVAWEB网页编程的B/S架构不同，网络编程是C/S编程

1.2 网络通信的要素

如何实现网络的通信？

通信双方的ip、端口号
规则：TCP/IP 、OSI

小结：

网络编程中两个主要的问题
- 如何准确定位到网络上一台或多台主机
- 找到主机之后如何进行通信
网络编程中的要素
- IP和端口号
- 网络通信协议 UDP TCP/IP
万物皆对象

1.3 IP

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 / ipv6
  - IPV4 127.0.0.1 四个字节组成已被用尽
  - IPV6 128位、8个无符号整数组成
    
    2834:4bba:aacb:0013:1241:1aaa:1341:6254
- 公网 (互联网）- 私网（局域网）
域名：记忆IP问题

获取相关信息

package com.company.lesson01;

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

// 测试IP
public class TestInetAddress {
    public static void main(String[] args) {
        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);

            // 查询网络地址
            InetAddress inetAddress2 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress2);
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

1.4 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 0 - 65535
TCP,UDP
端口分类
- 公有端口 0 - 1023
  - HTTP: 80
  - HTTPS: 443
  - FTP: 21
  - TELENT: 23
- 程序注册接口 1024 - 49151分配用户或者程序
  - Tomcat: 8080
  - MySQL: 3306
  - Oracle: 1521
- 动态、私有 49152 - 65535
```
netstat -ano # 查看所有端口
netstat -ano|findstr "****" # 查看指定端口
tasklist|findstr "****" # 查看指定端口的进程
```

package com.company.lesson01;

import java.net.InetSocketAddress;

public class TestInetSocketAddress {
    public static void main(String[] args) {
        InetSocketAddress socketAddress1 = new InetSocketAddress("127.0.0.1", 8080);
        InetSocketAddress socketAddress2 = new InetSocketAddress("localhost", 8080);
        System.out.println(socketAddress1);
        System.out.println(socketAddress2);

        System.out.println(socketAddress1.getAddress());
        System.out.println(socketAddress1.getHostName());
        System.out.println(socketAddress1.getPort());
    }
}

1.5 通信协议

协议：约定俗称的语音、符号

网络通信协议：速率、传输码率、代码结构、传输控制

TCP/IP协议簇

TCP: 用户传输协议
UDP: 用户数据报协议
IP: 网络互连协议

TCP / UDP对比

TCP：连接稳定、三次握手四次挥手、客户端与服务端、传输需要释放效率低

UDP: 不连接不稳定、客户端服务端无明确界限、无需准备、 DDOS洪泛攻击

1.6 TCP

客户端

1.连接服务器 Socket
2.发送消息

package com.company.lesson02;

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

// 客户端
public class TcpClientDemo01 {
    public static void main(String[] args) {

        Socket socket = null;
        OutputStream os = null;

        try {
            // 1. 知道 服务器地址
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            // 2. 创建一个socket链接
            socket = new Socket(serverIP, port);
            // 3. 发送消息 IO流
            os = socket.getOutputStream();
            os.write("hello world".getBytes());
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            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
等待用户的链接 accept
接收用户的消息

package com.company.lesson02;

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) throws IOException {

        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;

        try  {
            // 1. 创建一个地址
            serverSocket = new ServerSocket(9999);
            // 2. 等待客户端链接发送
            socket = serverSocket.accept();
            // 3. 读取客户端发送的消息
            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();
                }
            }
        }
    }
}

1.7 文件上传

客户端

package com.company.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链接
        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("pic.jpg"));
        //4. 写出文件
        byte[] buffer = new byte[1024];
        int len;
        while((len = fis.read(buffer)) != -1){
            os.write(buffer, 0, len);
        }

        // 通知服务器已经结束
        socket.shutdownOutput(); // 已经传输完毕

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

        byte[] buffer2 = new byte[2014];
        int len2;
        while((len2 = inputStream.read(buffer2)) != -1){
            baos.write(buffer2, 0, len2);
        }

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

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

服务端

package com.company.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 一直等待客户端
        // 3. 获取输入流
        InputStream is = socket.getInputStream();
        // 4. 文件输出
        FileOutputStream fos = new FileOutputStream(new File("receive.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,断开操作".getBytes());

        // 5. 关闭资源
        fos.close();
        is.close();
        socket.close();
        serverSocket.close();
    }
}

1.8 Tomcat

服务端

自定义 S
Tomcat服务器 S : JAVA后台开发

客户端

自定义 C
浏览器 B

1.9 UDP

发送消息

发送端

package com.company.lesson03;

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

// 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. 建包
        String msg = "hello world";
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;

        // 数据， 数据长度起始， 发送目的
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);

        // 3. 发送包
        socket.send(packet);
        // 关闭资源
        socket.close();
    }
}

接收端

package com.company.lesson03;

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

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(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(), 0, packet.getLength()));

        // 关闭资源
        socket.close();
    }
}

案例：咨询

发送方

package com.company.chat;

import javax.swing.plaf.synth.SynthTextAreaUI;
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 UdpSender {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(8888);
        // 准备数据 从控制台读取 system.in
        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();
    }
}

接收方

package com.company.chat;

import javax.xml.crypto.Data;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.time.chrono.IsoChronology;

public class UdpReceiver {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(6666);

        while(true){
            // prepare receive the packet
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container, 0, container.length);
            socket.receive(packet); // 阻塞式接收

            // 断开连接 bye
            byte[] data = packet.getData();
            String receiveData = new String(data, 0, data.length);
            System.out.println(receiveData);
            if (receiveData.equals("bye")) break;
        }
        socket.close();
    }
}

多线程：双方同时收发

接收方

package com.company.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() {
        try {
            while(true){
                // prepare receive the packet
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);
                socket.receive(packet); // 阻塞式接收

                // 断开连接 bye
                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();
    }
}

发送方

package com.company.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;
import java.util.concurrent.ExecutionException;

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){
            String data = null;
            try {
                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();
    }
}

多线程

package com.company.chat;

public class TalkStu {
    public static void main(String[] args) {
        // 开启两个线程
        new Thread(new TalkSend(7878, "localhost", 9988)).start();
        new Thread(new TalkReceive(8899, "teac")).start();
    }
}

package com.company.chat;

public class TalkTeac {
    public static void main(String[] args) {
        new Thread(new TalkSend(5555, "localhost", 8899)).start();
        new Thread(new TalkReceive(9988, "Stu")).start();
    }
}

2.0 URL

统一资源定位符：定位资源，定位互联网上的某一个资源

DNS域名解析

协议：// ip 地址：端口/ 项目名 / 资源

下载网络资源

package com.company.lesson03;

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

public class UrlDown {
    public static void main(String[] args) throws Exception {
        // 1. download Address
        URL url = new URL(""); // 网络资源地址
        // 2. connect HTTP
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("fileName.txt"); // 下来的命名

        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(); // 断开连接
    }
}

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原文地址：https://www.cnblogs.com/coderzjz/p/14303583.html