网路编程

1.1、网路编程的目的：

传播交流信息，数据交换，通信

要达到的效果：

1.如何准确的地位网络上的一台主机192.168.43.233:端口  定位到这个计算机上的某个资源

2.找到了这个主机，如何传输数据

 

javaweb：网页编程   B/S

网络编程： TCP/IP   C/S

 

1.2、网络通信的要素

如何实现网络的通信

通信双方地址：

• ip
• 端口号
• 192.168.43.233：端口号

规则：网络通信的协议

TCP/IP参考模型：

小结

1. 网络编程中有两个主要的问题
   • 如何准确的定位到网络上的一台或者多态主机
   • 如何进行通信
2. 网络编程中的要素
   • IP和端口号  IP
   • 网络通信协议  UDP、TCP
3. 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   4个字节组成，每个字节长度0~255，有42亿个(北美30亿个，亚洲4亿个)
    • ipv6  128位。8个无符号整数
    • 
  • 公网（互联网）/ 私网（局域网）
    • ABCDE类地址
      • 
      • 
    • 192.168.xxx.xx专门给组织内部使用的

java代码实现获取ip(InetAddress)

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

//测试ip
public class TestInetAddress {
    public static void main(String[] args) {
        try {

            //获得本机ip地址
            InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
            System.out.println(inetAddress1);

            InetAddress inetAddress2 = InetAddress.getByName("localhost");
            System.out.println(inetAddress2);

            InetAddress inetAddress3 = InetAddress.getLocalHost();
            System.out.println(inetAddress3);

            //获得百度网站ip地址
            InetAddress inetAddress0 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress0);

        } 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！
• 端口被规定 0~65535
• TCP端口和UDP端口，共有65535×2个端口号，同一协议下，端口号不能冲突
• 端口分类
  • 公有端口0~1023
    • HTTP：80
    • HTTPS：443
    • FTP：21
    • TELENT：23
  • 程序注册端口：1024~49151
    • Tomcat：8080
    • MySQL：3306
    • Oracle：1521
  • 动态、私有：49152~65535

dos命令查看占用端口：netstat -ano
dos命令查看指定端口：netstat -ano|findstr "8080"

java代码实现获取端口(socketAddress)

import java.net.InetSocketAddress;

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

        System.out.println("------------------------------------------");

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

1.5、通信协议

协议：约定，就好比我们现在说的是普通话

TCP/IP协议簇：实际上是一组协议

重要

• TCP：用户传输协议
• UDP：用户数据报协议

TCP：打电话

• 连接，稳定
• 三次握手、四次挥手

三次握手：
    A:你瞅啥
    B:瞅你咋地
    A:那干一架啊

四次挥手
    A:我要走了
    B:认真的？
    B:确定吗？
    A:确定

• 客户端、服务端
• 传输完成，就释放连接，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
• 导弹
• DDOS：洪水攻击，（饱和攻击）

1.6、TCP

客户端

1. 连接服务器Socket
2. 发送消息

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

public class TcpClient {

    public static void main(String[] args) {

        Socket socket = null;
        OutputStream os = null;

        try {
            //1.要知道服务器的地址,端口号
            InetAddress serverip = InetAddress.getByName("localhost");
            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，我是彭于晏".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

1. 建立服务的端口ServerSocket
2. 等待用户的连接accept
3. 接收用户的消息

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

public class TcpServer {
    public static void main(String[] args) {

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

        try {
            //1.得有一个地址
            serverSocket = new ServerSocket(9999);

            while (true){
                //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();
                //4.管道流
                baos = new ByteArrayOutputStream();
                
                //new一个缓存区
                byte[] buffer = new byte[1024];
                int len;
                //将is输出流中的东西写入缓存区
                while ( (len=is.read(buffer)) != -1){
                    //将缓存区的东西写入管道输出流中
                    baos.write(buffer, 0, len);
                }
                System.out.println(baos.toString());
            }


        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            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();
                }
            }

        }

    }
}

服务器端

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

//服务端接收文件
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，不然不会停

        //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());


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

    }
}

客户端

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

//客户端上传文件
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.获取文件
        FileInputStream fis = new FileInputStream(new File("lbj.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，我已经传输结束了
        socket.shutdownOutput();


        //确认服务器接收完毕，才能够断开连接
        InputStream is = socket.getInputStream();
        //String byte[]
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

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


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

    }
}

1.7、UDP

发短信：不用连接，需要知道对方的地址

客户端

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

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 = "你好服务器";
        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);

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

接收端

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

//还是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);

        socket.close();//阻塞接收，即永远活着等
        System.out.println(packet.getAddress().getHostName());
        System.out.println(new String(packet.getData()));
    }
}

循环发送消息

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

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[] 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();

    }
}

循环接收消息

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

            //收到bye就断开连接
            byte[] data = packet.getData();
            String receivedata = new String(data, 0, data.length);
            System.out.println(receivedata);

            if(receivedata.equals("bye")){
                break;
            }

        }
        socket.close();

    }
}

实现咨询功能，双方都能发送和接收消息

TalkSend类

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 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 (SocketException e) {
            e.printStackTrace();
        }
    }

    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 (Exception e) {
                e.printStackTrace();
            }
        }

        socket.close();
    }
}

TalkReceive类

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();
        }
    }

    public void run() {

        while (true){


            try {
                //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

                //收到bye就断开连接
                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();
    }
}

TalkStudent类

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();
    }
}

TalkTeacher类

public class TalkTeacher {
    public static void main(String[] args) {
        new Thread(new TalkSend(5555, "localhost", 8888)).start();
        new Thread(new TalkReceive(9999, "学生")).start();
    }
}

1.8、URL

统一资源定位符：定位互联网上某一个资源的

DNS域名解析  将域名www.baidu.com 解析成  xxx.xxx.xxx.xxx的ip

协议://ip地址:端口/项目名/资源

从网页上爬取音乐

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 IOException {

        //1.下载地址
        URL url = new URL("https://m10.music.126.net/20200111001152/d7b74120ccff288ba47ead8a76e01f7d/yyaac/520b/020c/0108/ea550af6055f208138876b652e8b52e4.m4a");

        //2.连接到这个资源 HTTP
        HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
        //获取输出流
        InputStream inputStream = urlConnection.getInputStream();
        //文件输出管道流
        FileOutputStream fos = new FileOutputStream("4.m4a");
        //缓存区
        byte[] buffer = new byte[1024];
        int len;
        while ((len = inputStream.read(buffer)) != -1){
            fos.write(buffer, 0, len);//写出这个数据
        }
        //关闭资源
        fos.close();
        inputStream.close();
        urlConnection.disconnect();
    }
}

bilibili:https://www.bilibili.com/video/av77704395