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Java零基础教程（十一.网络编程）

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1. 网络编程概述

2. 网络通信要素概述

3. 通信要素1：IP和端口号

4. 通信要素2：网络协议

5. TCP网络编程

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package com.atguigu.java1;

import org.junit.Test;

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

/*
实现TCP的网络编程
例子1：客户端
 */
public class TCPTest1 {
    // 客户端
    @Test
    public void client() {
        Socket socket = null;
        OutputStream os = null;
        try {
            // 1. 创建Socket对象，指明服务器端的ip和端口号
            InetAddress inet = InetAddress.getByName("192.168.1.66");//127.0.0.1或局域网ip
            socket = new Socket(inet, 8899);
            // 2. 获取一个输出流，用于输出数据
            os = socket.getOutputStream();
            // 3. 写出数据的操作
            os.write("你好，我是客户端mm".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // 4. 资源的关闭
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    // 服务端
    @Test
    public void server() {
        ServerSocket ss = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            // 1. 创建服务器端的ServerSocket，指明自己的端口号
            ss = new ServerSocket(8899);
            // 2. 调用accept()表示接收来自于客户端的socket
            socket = ss.accept();
            // 3. 获取输入流
            is = socket.getInputStream();
            // 4. 读取输入流中的数据
            baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[5];
            int len;
            while ((len = is.read(buffer)) != -1) {
                baos.write(buffer, 0, len);
            }
            System.out.println(baos.toString());
            System.out.println("收到了来自于：" + socket.getInetAddress() + "的数据");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (baos != null) {
                // 5. 关闭资源
                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 (ss != null) {
                try {
                    ss.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

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package com.atguigu.java1;

import org.junit.Test;

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

/*
例题2：客户端发送文件给服务端，服务端将文件保存在本地
 */
public class TCPTest2 {

    /*
    这里涉及的异常还是需要try-catch，这里throws偷懒
     */
    @Test
    public void client() throws IOException {
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9090);
        OutputStream os = socket.getOutputStream();
        FileInputStream fis = new FileInputStream(new File("disney.jpeg"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1) {
            os.write(buffer, 0, len);
        }
        fis.close();
        os.close();
        socket.close();
    }

    @Test
    public void server() throws IOException {

        ServerSocket ss = new ServerSocket(9090);
        Socket socket = ss.accept();
        InputStream is = socket.getInputStream();
        FileOutputStream fos = new FileOutputStream(new File("disney1.jpeg"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = is.read(buffer)) != -1) {
            fos.write(buffer, 0, len);
        }
        fos.close();
        is.close();
        socket.close();
        ss.close();
    }
}


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package com.atguigu.java1;

import org.junit.Test;

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

/*
实现TCP的网络编程

 */
public class TCPTest3 {

    /*
    这里涉及的异常还是需要try-catch，这里throws偷懒
     */
    @Test
    public void client() throws IOException {
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9090);
        OutputStream os = socket.getOutputStream();
        FileInputStream fis = new FileInputStream(new File("disney.jpeg"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1) {
            os.write(buffer, 0, len);
        }
        // 关闭数据输出，告知服务器端数据传完了
        socket.shutdownOutput();
        // 接受来自于服务器端的数据，并显示到控制台上
        InputStream is = socket.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer1 = new byte[20];
        int len1;
        while ((len1 = is.read(buffer1)) != -1) {
            baos.write(buffer1, 0, len1);
        }
        System.out.println(baos.toString());
        fis.close();
        os.close();
        socket.close();
        baos.close();
    }

    @Test
    public void server() throws IOException {

        ServerSocket ss = new ServerSocket(9090);
        Socket socket = ss.accept();
        InputStream is = socket.getInputStream();
        FileOutputStream fos = new FileOutputStream(new File("disney2.jpeg"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = is.read(buffer)) != -1) {
            fos.write(buffer, 0, len);
        }
        System.out.println("图片传输完成");
        // 服务器端给予客户端反馈
        OutputStream os = socket.getOutputStream();
        os.write("Disney is so beautiful!".getBytes());

        os.close();
        fos.close();
        is.close();
        socket.close();
        ss.close();
    }
}

6. UDP网络编程

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package com.atguigu.java1;

import org.junit.Test;

import java.io.IOException;
import java.net.*;

/*
UDP协议的网络编程
 */
public class UDPTest {
    @Test
    public void sender() throws IOException {
        DatagramSocket socket = new DatagramSocket();
        String str = "this is a UDP message";
        byte[] data = str.getBytes();
        InetAddress inet = InetAddress.getLocalHost();
        DatagramPacket packet = new DatagramPacket(data, 0, data.length, inet, 9090);
        socket.send(packet);
        socket.close();
    }

    @Test
    public void receiver() throws IOException {
        DatagramSocket socket = new DatagramSocket(9090);
        byte[] buffer = new byte[100];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
        socket.receive(packet);
        System.out.println(new String(packet.getData(), 0, packet.getLength()));
    }
}

7. URL编程

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package com.atguigu.java1;

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

/*
URL网络编程
1. URL: 统一资源定位符，对应着互联网的某一资源地址
2. 格式：
http://localhost:8080/examples/disney.jpeg?username=Tom
协议    主机名     端口号 资源地址              参数列表
 */
public class URLTest {
    public static void main(String[] args) {
        URL url = null;
        try {
            url = new URL("http://localhost:8080/examples/disney.jpeg?username=Tom");
            System.out.println(url.getProtocol());
            System.out.println(url.getHost());
            System.out.println(url.getPort());
            System.out.println(url.getPath());
            System.out.println(url.getFile());
            System.out.println(url.getQuery());
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }
}


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package com.atguigu.java1;

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

public class URLTest1 {
    public static void main(String[] args) {
        HttpURLConnection urlConnection = null;
        InputStream is = null;
        FileOutputStream fos = null;
        try {
            URL url = new URL("https://s3.amazonaws.com/cms.ipressroom.com/219/files/20149/544a6120f6091d588d000048_NVLogo_2D_H/NVLogo_2D_H_thmb.jpg");
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.connect();
            is = urlConnection.getInputStream();
            fos = new FileOutputStream("day10/nvidia_logo.jpg");
            byte[] buffer = new byte[1024];
            int len;
            while ((len = is.read(buffer)) != -1) {
                fos.write(buffer, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fos != null) {
                //关闭资源
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
        }
    }
}
Updated on 2021-08-22
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