[网络协议]java 网络编程

网络编程

• 计算机网络：将地理位置不同的具有独立功能的多台计算计算及其外部设备，通过通信线路连接起来，在网络操作系统，网络管理软件及网络通信协议的管理和协调下，实现资源共享和信息传递的计算机系统。
• 网络编程的目的：数据交换，通信
• 需要解决的问题：
  • 如何准确定位网络上的一台主机和这台主机的某个资源（ip + 端口号）
  • 找到主机后，如何传输数据？（网络通信协议（主要TCP，UDP））

1.1网络通信要素

• IP类：InetAddress

  • 本机ip(localhost):127.0.0.1
  • ip地址分类：IPV4，4个字节组成。IPV6：128位。8个无符号整数；
    • 公网（互联网）/私网（局域网）

• 域命：记忆IP问题

import java.net.InetAddress;
import java.net.UnknownHostException;

public class TestInetAddress {
    public static void main(String[] args) {
        //new InetAddress(); //无法new
        try {
            //查询本机IP地址
            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);

            //常用方法测试
            System.out.println(inetAddress1.getAddress());
            System.out.println(inetAddress1.getCanonicalHostName());
            System.out.println(inetAddress1.getHostAddress());
            System.out.println(inetAddress1.getHostName());

            //查询网站IP地址
            InetAddress inetAddress11 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress11);
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

• 端口：计算机程序进程相关；单协议下不同进程有不同的端口号（区分不同程序）；

  • TCP，UDP各有端口号：0-65535；

  • 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，分配给用户或程序
    • 动态、私有：49152-65535

import java.net.InetSocketAddress;

public class TestInetSocketAddress {
    public static void main(String[] args) {
        //查看端口号
        InetSocketAddress inetSocketAddress1 = new InetSocketAddress("127.0.0.1",8080);
        System.out.println(inetSocketAddress1);

        InetSocketAddress inetSocketAddress2 = new InetSocketAddress("localhost",8080);
        System.out.println(inetSocketAddress2);

        //常用方法
        System.out.println(inetSocketAddress1.getAddress());
        System.out.println(inetSocketAddress1.getHostName());//地址
        System.out.println(inetSocketAddress1.getHostString());
        System.out.println(inetSocketAddress1.getPort());//端口
    }
}

• 网络通信协议：速率，传输码率，代码结构，传输控制…

  • 太过复杂：分层—>TCP/IP协议簇

  • TCP：用户传输协议（类似打电话）

    • 连接，稳定
    • 三次握手，四次挥手

    最少需要三次，保证稳定连接
    A：你瞅啥？
    B：瞅你咋地？
    A：干一场
    
    挥手：
    A：我要走了
    B:你真的要走了吗？
    B：你真的真的要走了吗？
    A：我真的要走了！
    

    • 客户端，服务端
    • 传输完成，释放连接，效率低

  • UDP：用户数据包协议（类似发短信）

    • 不连接，不稳定
    • 客户端，服务段没有明确的界限
    • 不管有没有准备好，都可以发给你
    • DDoS攻击，饱和攻击

    TCP/IP

    客户端

    1. 连接服务器 Socket
    2. 发送消息

    服务器

    1.建立服务端口 ServerSocket

    2.等待用户的连接 accept

    3.接收用户的消息

    //服务器端
    public class TcpServerDemo1 {
        public static void main(String[] args) {
            ServerSocket serverSocket = null;//方便统一关闭资源
            Socket socket = null;
            InputStream is = null;
            ByteArrayOutputStream baos = null;
            try {
                //1.服务器得有一个地址
                serverSocket = new ServerSocket(9999);
                //2. 等待客户端连接过来
                socket = serverSocket.accept();//服务器方法accept()监听
                //3. 读取客户端的消息
                is = socket.getInputStream();
    
                /*
                * 一般读方法，不能超过1024，会出现乱码
                * byte[] buffer = new byte[1024];
                * int len;
                * while ((len = is.read(buffer)) != -1) {
                *     String msg = new String(buffer,0,le);
                *     System.out.println(msg);
                * }
                * */
    
                //使用管道流
                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 (IOException e) {
                e.printStackTrace();
            } finally {
                //关闭资源,无论项目多繁琐，先处理异常，保证项目正常进行
                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();
                    }
                }
            }
        }
    }
    

    //客户端
    public class TcpClientDemo1 {
        public static void main(String[] args) {
            Socket socket = null;
            OutputStream os = null;
            try {
                //1.要知道服务器的地址和端口号
                InetAddress inetAddress = InetAddress.getByName("127.0.0.1");
                int port = 9999;
                //2.创建一个 socket 连接
                socket = new Socket(inetAddress,port);
                //3. 发送消息 IO 流
                os = socket.getOutputStream();
                os.write("你好，欢迎学习Java".getBytes());
            } catch (Exception 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();
                    }
                }
            }
        }
    }
    

    TCP传输文件

    public class TcpClientDemo2 {
        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.文件流,读取文件
            FileInputStream fis = new FileInputStream(new File("ludashi.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，已经传输完毕
            socket.shutdownOutput();
    
            //确定服务器接收完毕，才能断开连接
            InputStream inputStream = socket.getInputStream();
            //String byte[]
            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());
    
            //5.关闭资源
            baos.close();
            inputStream.close();
            fis.close();
            os.close();
            socket.close();
        }
    }
    
    

    public class TcpServerDemo2 {
        public static void main(String[] args) throws IOException {
            //1.创建服务端口
            ServerSocket serverSocket = new ServerSocket(9000);
            //2.监听客户端的连接
            Socket socket = serverSocket.accept();//阻塞式监听，会一直等待
            //3.获取输入流
            InputStream is = socket.getInputStream();
            //4.文件输出
            FileOutputStream fos = new FileOutputStream(new File("receive.jpg"));
            byte[] buffer = new byte[1024];
            int len;
            while((len=is.read(buffer))!=-1) {
                fos.write(buffer,0,len);
            }
    
            //通知客户端接收完毕
            OutputStream os = socket.getOutputStream();
            os.write("我已接收完毕，你可以断开连接".getBytes());
    
            //关闭资源
            fos.close();
            is.close();
            socket.close();
            serverSocket.close();
        }
    }
    

    Tomcat

    服务端

    • 自定义服务S
    • Tomcat服务器S：（java后台开发）

    客户端

    • 自定义 C
    • 浏览器 B

    UDP

    类似发短信，不用建立连接，只要知道地址即可

    示例：UDP发送消息

    //UDP没有客户端，服务器，起名只是便于区分
    public class UdpServerDemo1 {
        public static void main(String[] args) throws Exception {
            //开放端口
            DatagramSocket socket = new DatagramSocket(9000);
            //接收数据包
            byte[] buffer = new byte[1024];
            DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
    
            socket.receive(packet);//阻塞式接收
            System.out.println(packet.getAddress().getHostAddress());
            System.out.println(new String(packet.getData(),0,packet.getLength()));
            //关闭连接
            socket.close();
        }
    }
    

    //UDP,不需要连接服务器
    public class UdpClientDemo1 {
        public static void main(String[] args) throws Exception {
            //1.建立一个Socket
            DatagramSocket socket = new DatagramSocket();
            //2.建立一个包
            String msg = "hello,Server!";
    
            //发送给谁
            InetAddress address = InetAddress.getByName("localhost");
            int port = 9000;
            //DatagramPacket(数据，数据的长度起始，发送给谁）
            DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,address,port);
            //3.发送包
            socket.send(packet);
    
            //4.关闭流
            socket.close();
        }
    }
    

    UDP咨询

    示例：循环发送和接收

    public class UdpReceiverDemo01 {
        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,data.length);
                System.out.println(receiveData);
                if(receiveData.equals("bye")) {
                    break;
                }
            }
            socket.close();
        }
    }
    

    public class UdpSenderDemo01 {
        public static void main(String[] args) throws Exception {
            DatagramSocket socket = new DatagramSocket(8888);
    
            //准备数据：从控制台读取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();
        }
    }
    

    示例：UDP多线程在线咨询

public class TalkSend implements Runnable{
    DatagramSocket socket = null;
    BufferedReader reader = null;

    private String toIP;
    private int toPort;
    private int fromPort;

    public TalkSend(String toIP, int toPort, int fromPort) {
        this.toIP = toIP;
        this.toPort = toPort;
        this.fromPort = fromPort;

        try {
            socket = new DatagramSocket(fromPort);
            reader = new BufferedReader(new InputStreamReader(System.in));
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    public TalkSend() {

    }

    @Override
    public void run() {
        while (true) {
            String data = null;
            try {
                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();
    }
}

public class TalkReceive implements Runnable{
    private int port;
    DatagramSocket socket = null;
    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,data.length);
                System.out.println(msgFrom +" ："+receiveData);
                if(receiveData.equals("bye")) {
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
        socket.close();
    }
}

public class TalkStudent {
    public static void main(String[] args) {
        new Thread(new TalkSend("localhost",9999,7777)).start();
        new Thread(new TalkReceive(8888,"teacher")).start();
    }
}

public class TalkTeacher {
    public static void main(String[] args) {
        new Thread(new TalkSend("localhost",8888,5555)).start();
        new Thread(new TalkReceive(9999,"student")).start();
    }
}

URL

URL:统一资源定位符，定位互联网上的某一个资源

1 协议: //ip地址：端口/项目名/资源

URL下载网络资源示例：下载网易云上的一副图片

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

//URL类示意
public class URLDemo {
    public static void main(String[] args) {
        URL url = null;
        try {
            url = new URL("http://localhost:8080/helloworld/index.jsp?username=jay&password=123");
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
        System.out.println(url.getProtocol());//协议
        System.out.println(url.getHost());//主机
        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下载网络资源
public class UrlDown {
    public static void main(String[] args) throws IOException {
        //1.下载地址
        URL url = new URL("https://p4.music.126.net/Nl4mFBPeN4Lqtqn3KOAvXQ==/109951166171044898.jpg?param=200y200");

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

        InputStream inputStream = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("test.jpg");
        byte[] buffer = new byte[1024];
        int len;
        while ((len=inputStream.read(buffer)) != -1) {
            fos.write(buffer,0,len);
        }

        //关闭资源
        fos.close();
        inputStream.close();
        urlConnection.disconnect();
    }
}