Java基础 - 第九章 - 网络编程

时间:2024-11-09 22:07:54

网络编程

网络通信协议

数据的封装和拆封

一、IP和端口号

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:          
                
    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

二、网络通信协议

TCP三次握手

TCP四次挥手

传输层的TCP协议和UDP协议的主要区别
    TCP:可靠的数据传输(三次握手);进行大数据量的传输;效率低
    UDP:不可靠;以数据报形式发送,数据报限定为64k;效率高

三、TCP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

@Test
    //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("192.168.1.107");
            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()); //你好,我是客户端mm
            System.out.println("收到了来自于:" + socket.getInetAddress().getHostAddress() + "的数据"); //收到了来自于:192.168.1.107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();
                }
            }
        }
    }

例题2: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。

@Test
    //客户端
    @Test
    public void client(){
        Socket socket = null;
        OutputStream os = null;
        FileInputStream fis = null;
        try {
            socket = new Socket(InetAddress.getByName("192.168.1.107"),9090);
            os = socket.getOutputStream();
            fis = new FileInputStream(new File(""));
            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();
            //接收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());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
        }
        if(fis != null){
            try {
                fis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if(os != null){
            try {
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if(socket != null){
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if(baos != null){
            try {
                baos.close();
            } catch (IOException e){
                e.printStactTrace();
            }
        }
    }

    //服务端
    @Test
    public void server(){
        ServerSocket ss = null;
        Socket socket = null;
        InputStream is = null;
        FileOutputStream fos = null;
        try {
            ss = new ServerSocket(9090);
            socket = ss.accept();
            is = socket.getInputStream();
            fos = new FileOutputStream(new File(""));
            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("你好,美女,照片我已收到,非常漂亮!".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
        }
        if(os != null){
            try {
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if(fos != null){
            try {
                fos.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();
            }
        }
    }

四、UDP网络编程

@Test

    //发送端
    @Test
    public void sender(){
        DatagramSocket socket = null;
        try {
            socket = new DatagramSocket();
            String str = "我是UDP方式发送的导弹";
            byte[] data = str.getBytes();
            InetAddress inet = InetAddress.getByName("192.168.1.107");
            DatagramPacket packet = new DatagramPacket(data,0,data.length,inet,9090);
            socket.send(packet);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            socket.close();
        }
    }

    //接收端
    @Test
    public void receiver(){
        DatagramSocket socket = null;
        try {
            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()));
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            socket.close();
        }
    }

五、URL编程

: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/?username=Tom
    协议   主机名    端口号  资源地址           参数列表

@Test

    @Test
    public void URLTest(){
        try {
            URL url = new URL("http://localhost:8080/examples/?username=Tom");

            //public String getProtocol()获取该URL的协议名
            System.out.println(url.getProtocol()); //http
            //public String getHost()获取该URL的主机名
            System.out.println(url.getHost()); //localhost
            //public String getPort()获取该URL的端口号
            System.out.println(url.getPort()); //8080
            //public String getPath()获取该URL的文件路径
            System.out.println(url.getPath()); ///examples/
            //public String getFile()获取该URL的文件名
            System.out.println(url.getFile()); ///examples/?username=Tom
            //public String getQuery()获取该URL的查询名
            System.out.println(url.getQuery()); //username=Tom
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }
    
    @Test
    public void URLTest1(){
        HttpURLConnection urlConnection = null;
        InputStream is = null;
        FileOutputStream fos = null;
        try {
            URL url = new URL("http://localhost:8080/examples/");
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.connect();
            is = urlConnection.getInputStream();
            fos = new FileOutputStream("day10\\");
            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 {
            //关闭资源
            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();
            }
        }
    }