Java开发：网络编程-优快云博客

本文链接：https://blog.youkuaiyun.com/android157/article/details/128047632

本文详细介绍了Java网络编程的基础知识，包括IP地址分类、端口概念、TCP与UDP协议的应用，以及Tomcat服务器的使用。通过示例展示了TCP连接、文件传输以及UDP双向通信的实现，并探讨了URL在网络编程中的作用。此外，还提供了URL下载网络图片的代码示例。

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记录Java网络编程相关知识，欢迎大家沟通交流

一、IP

Ip地址：InetAddress类

唯一定义一台网络上的计算机。
127.0.0.1：本机localhost

ip地址的分类：

1、ipv4/ipv6

ipv4 127.0.0.1 ， 4个字节组成，0~255 ，共42亿个，2001年就用尽了
ipv6 128位，8个无符号整数（2001:0bb2:aaaa:0015:0000:0000:1aaa:1213）

2、公网（互联网）-私网（局域网）

ABCD类地址
192.168.xxx.xxx：专给组织内部使用

域名：

解决记忆IP问题，方便记忆，最终域名会映射到IP上。

三个获取IP地址的方法

            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);

二、端口

端口表示计算机上一个程序的进程。

A. 不同的进程有不同的端口号，用来区分软件。

B. 端口号范围：0~65535

C. 端口分类

公有端口（系统使用或者是其他协议默认端口）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

三、TCP

客户端：
1、连接服务器Socket
2、发送消息

服务端：
1、建立服务端的端口 ServerSocket
2、等待用户的连接 accept
3、接收消息

收发消息示例



/**
 * 客户端
 */
public class TCPClient {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream outputStream = null;
        try {
            InetAddress localHost = InetAddress.getLocalHost();
            int port = 9999;
            socket = new Socket(localHost, port);
            outputStream = socket.getOutputStream();
            outputStream.write("你好，世界！".getBytes());
            outputStream.flush();
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            try {
                if (outputStream != null) {
                    outputStream.close();
                }
                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
    }
}



/**
 * 服务端
 */
public class TCPServer {

    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket accept = null;
        InputStream inputStream = null;
        ByteArrayOutputStream byteArrayOutputStream = null;
        try {
            serverSocket = new ServerSocket(9999);


            while (true) {
                accept = serverSocket.accept();
                inputStream = accept.getInputStream();
                byteArrayOutputStream = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024];
                int len;
                while ((len = inputStream.read(buffer)) != -1) {
                    byteArrayOutputStream.write(buffer, 0, len);
                }
                System.out.println(byteArrayOutputStream.toString());
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            try {
                byteArrayOutputStream.close();
                inputStream.close();
                accept.close();
                serverSocket.close();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
}

TCP上传文件流

在项目的根目录下拷贝client.jpg图片


/**
 * 服务器
 */
public class TCPUploadFileServer {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(9999);
            Socket accept = serverSocket.accept();
            InputStream inputStream = accept.getInputStream();
            FileOutputStream fileOutputStream = new FileOutputStream(new File("receive.jpg"));
            byte[] buffer = new byte[1024];
            int len;
            while ((len = inputStream.read(buffer)) != -1) {
                fileOutputStream.write(buffer, 0, len);
            }
            fileOutputStream.flush();

            OutputStream outputStream = accept.getOutputStream();
            outputStream.write("服务端接收完毕".getBytes());
            outputStream.flush();

            outputStream.close();
            fileOutputStream.close();
            inputStream.close();
            accept.close();
            serverSocket.close();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

/**
 * 客户端
 */
public class TCPUploadFileClient {
    public static void main(String[] args) {
        try {
            InetAddress host = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            Socket socket = new Socket(host, port);
            OutputStream outputStream = socket.getOutputStream();
            FileInputStream fileInputStream = new FileInputStream(new File("client.jpg"));
            byte[] buffer = new byte[1024];
            int len;
            while ((len = fileInputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, len);
            }
            outputStream.flush();

            //通知服务器输出流传输完毕
            socket.shutdownOutput();

            InputStream inputStream = socket.getInputStream();
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            byte[] iBuffer = new byte[1024];
            int ilen;
            while ((ilen = inputStream.read(iBuffer)) != -1) {
                byteArrayOutputStream.write(iBuffer, 0, ilen);
            }
            System.out.println(byteArrayOutputStream.toString());

            fileInputStream.close();
            outputStream.close();
            socket.close();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

四、Tomcat

服务端
1、自定义（S端）
2、Tomcat服务器（S端）:java后台开发

客户端
1、自定义（C端）
2、浏览器（B端）

五、UDP

UDP不存在服务端、客户端的概念，可以互相发送

public class UDPClient {
    public static void main(String[] args) {
        try {
            DatagramSocket socket = null;

            socket = new DatagramSocket();

            InetAddress host = InetAddress.getByName("127.0.0.1");
            int port = 9090;
            String msg = "你好啊，服务器";
            DatagramPacket datagramPacket = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, host, port);

            socket.send(datagramPacket);

            socket.close();

        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

public class UDPServer {
    public static void main(String[] args) {
        {
            try {
                DatagramSocket socket = null;

                socket = new DatagramSocket(9090);

                byte[] buffer = new byte[1024];
                DatagramPacket datagramPacket = new DatagramPacket(buffer, 0, buffer.length);

                socket.receive(datagramPacket);

                System.out.println(datagramPacket.getAddress().getHostAddress());
                System.out.println(new java.lang.String(datagramPacket.getData(), 0, datagramPacket.getLength()));

                socket.close();

            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
}

六、URL

http://www.baidu.com/
统一资源定位符：用于定位资源，定位互联网上的某一个资源。
DNS域名解析：把域名解析成 IP+Port
URL组成结构：协议：//IP地址：端口/项目名/资源


/**
 * URL网络编程，常用api示例
 */
public class URLDemo001 {
    public static void main(String[] args) {
        try {
            URL url = new URL("http://localhost:8080/helloworld/index.jsp?username=xiaowu&password=123");
            System.out.println(url.getProtocol());//协议
            System.out.println(url.getHost());//主机名
            System.out.println(url.getPort());//端口
            System.out.println(url.getPath());//文件相对路径
            System.out.println(url.getFile());//全路径
            System.out.println(url.getQuery());//参数
        } catch (MalformedURLException e) {
            throw new RuntimeException(e);
        }
    }
}

/**
 * URL网络编程，下载网络图片
 */
public class URLDemo001 {
    public static void main(String[] args) {
        try {
            URL url = new URL("https://www.baidu.com/img/PCtm_d9c8750bed0b3c7d089fa7d55720d6cf.png");
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            InputStream inputStream = urlConnection.getInputStream();
            //文件会下载到根目录下（项目根目录）
            FileOutputStream fileOutputStream = new FileOutputStream(new File("baidu.png"));
            byte[] buffer = new byte[1024];
            int len;
            while ((len = inputStream.read(buffer)) != -1) {
                fileOutputStream.write(buffer, 0, len);
            }
            fileOutputStream.flush();

            fileOutputStream.close();
            inputStream.close();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

                                       **end**