网络编程及练习

定义：

在网络通信协议下，不同计算机上运行的程序进行的数据传输。计算机和计算机之间通过网络进行数据传输

可以使用在java.net包下的技术开发出常见的网络应用程序

常见的软件架构：

C/S: Client/Server 客户端/服务器在用户本地需要下载并安装客户端程序，在远程有一个服务器端程序

优点：画面精美，用户体验好

缺点：需要开发客户端，也需要开发服务端，用户需要下载和更新的时候太麻烦

B/S：Browser/Server 只需要一个浏览器，用户通过不同的网址，客户访问不同的服务器

优点：不需要开发客户端，只需要页面+服务端；用户不需要下载，打开浏览器就能使用；

缺点：如果应用过大，用户体验会受影响

三要素：IP 端口号协议

IP：

设备在网络中的地址，是唯一的标识

定义：

全称：Internet Protocol，是互联网协议地址，也称IP地址，是分配给上网设备的数字标签，通俗理解：上网设备在网络中的地址，是唯一的

端口号：

应用程序在设备中唯一的标识

由两个字节表示的整数，取值范围：0~65535，其中0~1023之间的端口号用于一些知名的网络服务或者应用，自己使用1024以上的端口号就可以了

注意：一个端口号只能被一个应用程序使用

协议：

数据在网络中传输的规则，常见的协议有UDP，TCP，http,https,ftp

OSI参考模型：世界互联协议标准，全球通信规范，

TCP/IP参考模型（TCP/IP协议）：事实上的国际标准

图来自黑马程序员网课

TCP协议：传输控制协议（Transmission Control Protocol），它是面向连接通信协议，速度慢，没有大小限制，数据安全

TCP通信协议是一种可靠的网络协议，它在通信的两端各建立一个Socket对象，通信之前要保证连接已经建立，通过Socket产生IO流来进行网络通信

图来自黑马程序员网课

客户端代码：

package com.lazyGirl.netdemo.tcpdemo;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;

public class Client {
    public static void main(String[] args) throws IOException {

        //在创建该对象的同时会连接服务端，如果连不上，代码会报错
        Socket socket = new Socket("127.0.0.1",10086);

        //可以从连接通道中获取输出流
        OutputStream os = socket.getOutputStream();
        os.write("你好".getBytes());

        os.close();
        socket.close();
    }
}

服务端代码：

package com.lazyGirl.netdemo.tcpdemo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    public static void main(String[] args) throws IOException {

        ServerSocket serverSocket = new ServerSocket(10086);

        Socket socket = serverSocket.accept();

//        InputStream inputStream = socket.getInputStream();
//        InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
//        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);


        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));

        int b;
        while ((b = br.read()) != -1) {
            System.out.print((char) b);
        }

        socket.close();
        serverSocket.close();

    }
}

输出：

UDP协议：用户数据报协议（User Datagram Protocol），它是面向无连接通信协议，速度快，有大小限制，一次最多发送64K，数据不安全，易丢失数据

图来自黑马程序员网课

UDP的三种通信方式：

单播：

组播：组播地址：224.0.0.0 ~ 239.255.255.255 其中224.0.0.0 ~ 224.0.0.255为预留的组播地址

接收端1：

package com.lazyGirl.netdemo.udpdemo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

public class ReceiveMessageDemo {
    public static void main(String[] args) throws IOException {

        MulticastSocket ms = new MulticastSocket(10086);

        InetAddress group = InetAddress.getByName("224.0.0.1");
        ms.joinGroup(group);
        byte[] buf = new byte[1024];
        DatagramPacket dp = new DatagramPacket(buf, buf.length);
        ms.receive(dp);

        byte[] data = dp.getData();
        int len = data.length;
        String ip = dp.getAddress().getHostAddress();
        String name = dp.getAddress().getHostName();

        System.out.println("ip: " + ip + " name: " + name + " len: " + len + " data: " + new String(data));

        ms.close();

    }
}

发送端：

package com.lazyGirl.netdemo.udpdemo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

public class SendMessageDemo {
    public static void main(String[] args) throws IOException {

        MulticastSocket ms = new MulticastSocket();

        String s = "hello";
        byte[] buf = s.getBytes();
        InetAddress addr = InetAddress.getByName("224.0.0.1");
        int port = 10086;

        DatagramPacket dp = new DatagramPacket(buf, buf.length, addr, port);
        ms.send(dp);
        ms.close();


    }
}

输出：

两个接收端都接收到了消息

图来自黑马程序员网课

广播：255.255.255.255

将上面的地址改成255.255.255.255即实现该局域网内所有主机都收到消息

常见的CMD命令：

ipconfig: 查看本机ip地址

ping: 检查网络是否连通

InetAddress:

接收端：

package com.lazyGirl.netdemo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

public class ReceiveMessageDemo {
    public static void main(String[] args) throws IOException {


        //必须指定端口，且跟发送端口一致
        DatagramSocket socket = new DatagramSocket(10086);


        byte[] buf = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buf, buf.length);
        socket.receive(packet);

        byte[] data = packet.getData();
        int len = packet.getLength();
        InetAddress address = packet.getAddress();
        int port = packet.getPort();

        System.out.println("data " + new String(data,0,data.length));
        System.out.println("address " + address.getHostAddress());
    }
}

receive函数会阻塞

发送端：

package com.lazyGirl.netdemo;

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

public class SendMessageDemo {
    public static void main(String[] args) throws IOException {

        DatagramSocket socket = new DatagramSocket();

        String str = "hello";
        byte[] buf = str.getBytes();

        InetAddress address = InetAddress.getByName("192.168.1.111");

        int port = 10086;
        DatagramPacket packet = new DatagramPacket(buf, buf.length, address, port);

        socket.send(packet);

        socket.close();
    }
}

输出：

聊天室：

发送端：

package com.lazyGirl.netdemo.netcase1;

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

public class SendMessageDemo {
    public static void main(String[] args) throws IOException {

        DatagramSocket socket = new DatagramSocket();

        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("Enter your message");
            String message = scanner.nextLine();

            if ("886".equals(message)) {
                break;
            }

            byte[] data = message.getBytes();

            InetAddress address = InetAddress.getByName("lazyGril");

            int port = 10086;

            DatagramPacket packet = new DatagramPacket(data, data.length, address, port);

//            System.out.println("Sending Message");

            socket.send(packet);
        }

        socket.close();

    }
}

接收端：

package com.lazyGirl.netdemo.netcase1;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class ReceiveMessageDemo {
    public static void main(String[] args) throws IOException {


        DatagramSocket socket = new DatagramSocket(10086);

        byte[] buf = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buf, buf.length);

        while (true) {
            socket.receive(packet);
            byte[] data = packet.getData();
            int len = packet.getLength();
            int port = packet.getPort();
            String ip = packet.getAddress().getHostAddress();
            String name = packet.getAddress().getHostName();

            System.out.println("ip: " + ip + " name: " + name + " port: " + port + " len: " + len + " data: " + new String(data));
        }

    }
}

输出：

练习：

case1:

客户端：发送一条数据，接收服务端反馈的消息并打印

服务器：接收数据并打印，再给客户端反馈消息

线程池版：

客户端：

package com.lazyGirl.netdemo.test3;

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

public class Client {
    public static void main(String[] args) throws IOException {

        Socket socket = new Socket("127.0.0.1",10086);
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream("a.txt"));
        BufferedOutputStream bos = new BufferedOutputStream(socket.getOutputStream());
        byte[] buf = new byte[1024];
        int len;
        while ((len = bis.read(buf)) != -1) {
            bos.write(buf, 0, len);
        }
        socket.shutdownOutput();

        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String str = br.readLine();
        System.out.println(str);

        socket.close();
    }
}

服务端：

package com.lazyGirl.netdemo.test3;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.UUID;
import java.util.concurrent.*;

public class Server {
    public static void main(String[] args) throws IOException {

        ThreadPoolExecutor pool = new ThreadPoolExecutor(
                3,
                16,
                60,
                TimeUnit.SECONDS,
                new ArrayBlockingQueue<>(2),
                Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.AbortPolicy()
        );

        ServerSocket serverSocket = new ServerSocket(10086);
        while (true) {
            Socket socket = serverSocket.accept();
            pool.submit(new MyRunnable(socket));

        }
    }
}

package com.lazyGirl.netdemo.test3;

import java.io.*;
import java.net.Socket;
import java.util.UUID;

public class MyRunnable implements Runnable {

    Socket socket;
    public MyRunnable(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try{
            BufferedInputStream bis = new BufferedInputStream(socket.getInputStream());
            String name = UUID.randomUUID().toString().toString().replaceAll("-", "");
            BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(name + ".txt"));
            int len;
            byte[] buf = new byte[1024];
            while ((len = bis.read(buf)) != -1) {
                bos.write(buf, 0, len);
            }

            BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
            bw.write("上传成功");
            bw.newLine();
            bw.flush();
            bw.close();
        }catch (IOException e){
            e.printStackTrace();
        }finally {
            if(socket != null){
                try {
                    socket.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }
}

输出：