Java网络编程

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1.网络通信概述

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2. 通信要素1：IP和端口号

2.1 IP和端口号

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2.2 InetAddress 类

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2.3 代码示例

/**
 *
 * 一、网络编程中有两个主要的问题：
 * 1.如何准确地定位网络上一台或多台主机；定位主机上的特定的应用
 * 2.找到主机后如何可靠高效地进行数据传输
 *
 * 二、网络编程中的两个要素：
 * 1.对应问题一：IP和端口号
 * 2.对应问题二：提供网络通信协议：TCP/IP参考模型（应用层、传输层、网络层、物理+数据链路层）
 *
 *
 * 三、通信要素一：IP和端口号
 *
 * 1. IP:唯一的标识 Internet 上的计算机（通信实体）
 * 2. 在Java中使用InetAddress类代表IP
 * 3. IP分类：IPv4 和 IPv6 ; 万维网 和 局域网
 * 4. 域名:   www.baidu.com   www.mi.com  www.sina.com  www.jd.com
 *            www.vip.com
 * 5. 本地回路地址：127.0.0.1 对应着：localhost
 *
 * 6. 如何实例化InetAddress:两个方法：getByName(String host) 、 getLocalHost()
 *        两个常用方法：getHostName() / getHostAddress()
 *
 * 7. 端口号：正在计算机上运行的进程。
 * 要求：不同的进程有不同的端口号
 * 范围：被规定为一个 16 位的整数 0~65535。
 *
 * 8. 端口号与IP地址的组合得出一个网络套接字：Socket
 * @ClassName : InetAddressTest  
 * @Description :   
 * @Author : Yemulin  
 * @Date : 2020/03/25 20:43  
 * @Version : 1.0
 */

public class InetAddressTest {

    public static void main(String[] args) {

        try {
            InetAddress inet1 = InetAddress.getByName("192.168.10.14");
            System.out.println(inet1);

            InetAddress inet2 = InetAddress.getByName("www.baidu.com");
            System.out.println(inet2);

            InetAddress inet3 = InetAddress.getByName("127.0.0.1");
            System.out.println(inet3);

            //获取本地ip
            InetAddress inet4 = InetAddress.getLoopbackAddress();
            System.out.println(inet4);

            //getHostName()
            System.out.println(inet2.getHostName());
            //getHostAddress()
            System.out.println(inet2.getHostAddress());

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

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3. 通信要素2：网络协议

3.1 网络协议概述

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3.2 TCP网络编程

3.3 TCP网络编程三道例题

3.3.1 例一：

/**
 *
 * 实现TCP的网络编程
 * 例子1：客户端发送信息给服务端，服务端将数据显示在控制台上
 * @ClassName : TCPTest1  
 * @Description :   
 * @Author : Yemulin  
 * @Date : 2020/03/26 01:19  
 * @Version : 1.0
 */

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("127.0.0.1");
            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();

            //4.资源的关闭
        } 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();

            //不建议这样写，可能会有乱码
//        byte[] buffer = new byte[20];
//        int len;
//        while ((len = is.read(buffer)) != -1){
//            String str = new String(buffer,0,len);
//            System.out.print(str);
//        }

            //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().getHostAddress() + "的数据");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //5.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 (ss != null) {
                try {
                    ss.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }
}

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3.3.2 例二：

/**
 * 实现TCP的网络编程
 * 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。
 *
 * @ClassName : TCPTest2  
 * @Description :   
 * @Author : Yemulin  
 * @Date : 2020/03/26 15:33  
 * @Version : 1.0
 */

public class TCPTest2 {

    /*
    这里涉及到的异常，应该使用try-catch-finally处理
    */
    @Test
    public void client() throws IOException {
        //1.
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"),9090);
        //2.
        OutputStream os = socket.getOutputStream();
        //3.
        FileInputStream fis = new FileInputStream("picture.png");
        //4.
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1){
            os.write(buffer,0,len);
        }
        //5.
        fis.close();
        os.close();
        socket.close();

    }


    @Test
    public void server() throws IOException {
        //1.
        ServerSocket ss = new ServerSocket(9090);
        //2.
        Socket socket = ss.accept();
        //3.
        InputStream is = socket.getInputStream();
        //4.
        FileOutputStream fos = new FileOutputStream("picture1.png");
        //5.
        byte[] buffer = new byte[1024];
        int len ;
        while ((len = is.read(buffer)) != -1){
            fos.write(buffer,0 ,len);
        }
        //6.
        fos.close();
        is.close();
        socket.close();
        ss.close();
    }
}

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3.3.3 例三：

/**
 * 实现TCP的网络编程
 * 例题3：从客户端发送文件给服务端，服务端保存到本地。并返回“发送成功”给客户端。
 * 并关闭相应的连接。
 *
 * @ClassName : TCPTest3  
 * @Description :   
 * @Author : Yemulin  
 * @Date : 2020/03/26 17:40  
 * @Version : 1.0
 */

public class TCPTest3 {

    /*
    这里涉及到的异常，应该使用try-catch-finally处理
    */
    @Test
    public void client() throws IOException {
        //1.
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"),9090);
        //2.
        OutputStream os = socket.getOutputStream();
        //3.
        FileInputStream fis = new FileInputStream("picture.png");
        //4.
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1){
            os.write(buffer,0,len);
        }
        //关闭数据的输出
        socket.shutdownOutput();

        //5.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());
        //6.
        fis.close();
        os.close();
        socket.close();
        baos.close();
        is.close();

    }


    @Test
    public void server() throws IOException {
        //1.
        ServerSocket ss = new ServerSocket(9090);
        //2.
        Socket socket = ss.accept();
        //3.
        InputStream is = socket.getInputStream();
        //4.
        FileOutputStream fos = new FileOutputStream("picture2.png");
        //5.
        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");

        //6.服务器端给予客户端反馈
        OutputStream os = socket.getOutputStream();
        os.write("你好，照片已经收到".getBytes());

        //7.
        fos.close();
        is.close();
        socket.close();
        ss.close();
        os.close();

    }
}

3.4 UDP网络通信

3.4.1 DatagramSocket&DatagramPacket 的常用方法

3.4.2 代码演示

/**
 *
 * UDPd协议的网络编程
 * @ClassName : UDPTest  
 * @Description :   
 * @Author : Yemulin  
 * @Date : 2020/03/26 23:23  
 * @Version : 1.0
 */

public class UDPTest {

    //发送端
    @Test
    public void sender() throws IOException {

        DatagramSocket socket = new DatagramSocket();

        java.lang.String str = "我是UDP方式发送的导弹";
        byte[] data = str.getBytes();
        InetAddress inet = InetAddress.getLocalHost();
        DatagramPacket packet = new DatagramPacket(data,0,data.length,inet,9090);

        socket.send(packet);

        socket.close();

    }

    //接收端
    @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()));

        socket.close();
    }
}

3.5 URL编程

public class URLTest1 {

    public static void main(String[] args)  {

        HttpURLConnection urlConnection = null;
        InputStream is = null;
        FileOutputStream fos = null;
        try {
            URL url = new URL("http://localhost:8080/examples/picture.png");
            urlConnection = (HttpURLConnection) url.openConnection();

            urlConnection.connect();

            is = urlConnection.getInputStream();

            fos = new FileOutputStream("day10\\picture3.png");
            byte[] buffer = new byte[1024];
            int len;
            while ((len = is.read(buffer)) != -1){

                fos.write(buffer,0,len);
            }
            System.out.println("下载完成");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (urlConnection != null)
                urlConnection.disconnect();
        }

    }
}