Java网络编程

网络编程

1.1、概述

网络编程的目的：

无线电台...传播交流信息，数据交换。通信

想要达到这个效果需要什么：

如何准确的定位网络上的一台主机 192.168.16.124：端口，定位到这个计算机上的某个资源
找到了这个主机，如何传输数据呢？

javaWeb：网页编程 B/S

网络编程： TCP/IP C/S

1.2、网络通信的要素

网络编程中有两个主要问题

如何准确的定位到网络上的一台或者多台主机
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 IP
网络通信协议 UDP TCP

万物皆对象

1.3、IP

ip地址：InetAddress

唯一定位一台网络上计算机
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，0~255
  - IPV6 128位，8个无符号整数！
  例如：
```
2001:0bb2:aaaa:0015:0000:0000:1aaa:1312
```
- 公司（互联网）-- 私网（局域网）
  - ABCD类地址
  - 192.168.xx.xx，专门给组织内部使用的
域名：记忆IP问题！
- IP：www.vip.com

package com.yehuan.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，或者自己电脑的名字

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

1.4、端口

端口：InetSocketAddress

端口表示计算机是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：65535*2 tcp：80，udp：80 ，单个协议下，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，分配用户或者程序
  - Tomcat:8080
  - MySQL:3306
  - Oracle :1521
- 动态、私有：49152-65535
```
netstat -ano #查看所有的端口
netstat -ano|findstr "5900" #查看指定的端口
tasklist|findstr "8689" #查看指定端口的进程
Ctrl+shift+Esc
```

package com.yehuan.lesson01;

import java.net.InetSocketAddress;

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

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

1.5、通信协议

协议：约定，就好比我们现在说的是普通话

网络通信协议：速率，传输码率，代码结构，传输控制....

问题：非常复杂

大事化小：分层

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

出名的协议：

TCP
IP：网络互连协议

TCP和UDP对比：

TCP：打电话

连接，稳定
三次握手，四次挥手
客户端、服务段
传输完成，释放连接，效率低

UDP：发短信

不连接，不稳定
客户端、服务器：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

连接服务器Socket
发送消息

package com.yehuan.lesson02;

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.要知道服务器的地址，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("昼冷夜欢".getBytes());

        } catch (IOException 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
等待用户的连接 accept
接收用户消息

package com.yehuan.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) {
        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);

            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();
                //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 (Exception 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();
                }
            }

        }
    }
}

文件上传

服务器端：

package com.yehuan.lesson02;

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();
        //3.获取输入流
        InputStream is = socket.getInputStream();
        //4.文件输出
        FileOutputStream fos = new FileOutputStream("src\\seceive.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了
        OutputStream os = socket.getOutputStream();
        os.write("我接收完毕了，可以断开了".getBytes());

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

    }
}

客户端：

package com.yehuan.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.读写文件
        FileInputStream fis = new FileInputStream(new File("src\\1001.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，我已经传输完了
        socket.shutdownOutput();

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

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

}

Tomcat

服务器

自定义
Tomcat服务器

客户端

自定义
浏览器

1.7、UDP

发短信：不用连接，需要知到对方的地址

发送消息

发送端：

package com.yehuan.lesson03;

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

//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 = "你好，服务器!";
        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;
        //数据，数据长度起始，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
        socket.close();

    }
}

接收端：

package com.yehuan.lesson03;

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);//阻塞接收

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

        //关闭连接
        socket.close();
    }
}

咨询

发送方：

package com.yehuan.chat;

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();
    }
}

接收方：

package com.yehuan.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
            //断开连接 bye
            byte[] data = packet.getData();
            String receiveData = new String(data,0,packet.getLength());
            System.out.println(receiveData);
            if(receiveData.equals("bye")){
                break;
            }

        }
        socket.close();
    }
}

在线咨询：两个人都可以是发送方，也都可以是接收方！（多线程）

发送：

package com.yehuan.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.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();
        }
    }

    @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 (Exception e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

接收：

package com.yehuan.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) {
            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
                //断开连接 bye
                byte[] data = packet.getData();
                String receiveData = new String(data,0,packet.getLength());
                System.out.println(msgFrom+":"+receiveData);
                if(receiveData.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

学生：

package com.yehuan.chat;

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();
    }
}

老师：

package com.yehuan.chat;

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

package com.yehuan.lesson04;

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

public class URLDemo01 {
    public static void main(String[] args) throws Exception {
        URL url = new URL("http://localhost:8080/helloworld/index.jsp?username=yehuan&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
    }
}

URL下载网上资源

package com.yehuan.lesson04;

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

public class URLDown {
    public static void main(String[] args) throws Exception {
        //1.下载地址
        URL url = new URL("http://localhost:8080/yehuan/SecurityFile.txt");

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

        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("SecurityFile.txt");

        byte[] buffer = new byte[1024];
        int len;
        while ((len = inputStream.read(buffer)) != -1) {
            fos.write(buffer, 0, len);
        }
        fos.close();
        inputStream.close();
        urlConnection.disconnect();//断开连接
    }
}

posted @ 2025-02-18 21:17 昼冷夜欢阅读(2) 评论(0) 编辑收藏举报

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