Java后端笔记15

网络编程

三要素：协议、IP地址、端口号

TCP

TCP是一个面向连接的通信协议，需要完成“三次握手”才能通信

套接字socket使用

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * Create by xiye on 2019/12/6 14:40
 */
public class Server {
    /*
    * 服务端使用ServerSocket
    * */
    public static void main(String[] args) throws IOException {   
        // 设置一个监听端口，供客户端访问
        ServerSocket socket = new ServerSocket(1314);
        System.out.println("服务已开启...");

        Socket server = socket.accept();        // 阻塞，等待客户端接收
        String host = getHost(server);

        // 获取客户端请求内容
        InputStream is = server.getInputStream();
        byte[] b = new byte[128];
        int len = is.read(b);
        String req = new String(b, 0, len);
        System.out.println(host + "：" + req);
        // 返回信息
        OutputStream os = server.getOutputStream();
        os.write(req.getBytes());

        os.close();
        is.close();
        server.close();
    }

    /**
     * 获取IP地址和端口号拼接字符串
     * @param socket 套接字对象
     * @return IP地址:端口
     */
    private static String getHost(Socket socket) {
        return socket.getInetAddress().getHostAddress() + ":" + socket.getPort();
    }
}

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Scanner;

/**
 * Create by xiye on 2019/12/6 14:43
 */
public class Client {
    /*
    * 客户端使用Socket
    * */
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        // 连接服务端IP和端口
        Socket client = new Socket("192.168.31.103", 1314);

        // String str = "Nice to meet you~^_^~";
        String str = sc.next();
        OutputStream os = client.getOutputStream();
        // 发送
        os.write(str.getBytes());
        // 接收回返消息
        InputStream is = client.getInputStream();
        if (is != null) {
            String host = getHost(client);
            byte[] b = new byte[128];
            int len = is.read(b);
            System.out.print(host + "回复您：" + new String(b, 0, len));
        }
        is.close();
        os.close();

        client.close();
        sc.close();
    }

    /**
     * 获取IP地址和端口号拼接字符串
     * @param socket 套接字对象
     * @return IP地址:端口
     */
    private static String getHost(Socket socket) {
        return socket.getInetAddress().getHostAddress() + ":" + socket.getPort();
    }
}

TCP单一聊天实现
服务端

package com.xiye.single;

import com.xiye.single.thread.Receive;
import com.xiye.single.thread.Send;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * Create by xiye on 2019/12/6 16:42
 */
public class ServerTCP {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(1314);
        System.out.println("服务端开启....");

        Socket socket = serverSocket.accept();
        new Thread(new Receive(socket)).start();
        new Thread(new Send(socket)).start();
    }
}

客户端

package com.xiye.single;

import com.xiye.single.thread.Receive;
import com.xiye.single.thread.Send;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * Create by xiye on 2019/12/6 16:42
 */
public class ClientTCP {

    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("192.168.31.103", 1314);

        new Thread(new Receive(socket)).start();
        new Thread(new Send(socket)).start();
    }
}

发送线程

package com.xiye.single.thread;

import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Scanner;

/**
 * Create by xiye on 2019/12/6 16:42
 */
public class Send implements Runnable {

    private Socket socket;

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

    @Override
    public void run() {
        while (true) {
            synchronized (this) {
                if (socket != null) {
                    Scanner sc = new Scanner(System.in);
                    System.out.print("聊天内容：");
                    try {
                        OutputStream os = socket.getOutputStream();
                        os.write(sc.nextLine().getBytes());
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    private static String getHost(Socket socket) {
        return socket.getInetAddress().getHostAddress() + ":" + socket.getPort();
    }
}

接收线程

package com.xiye.single.thread;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.util.Scanner;

/**
 * Create by xiye on 2019/12/6 16:42
 */
public class Receive implements Runnable {

    private Socket socket;

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

    @Override
    public void run() {
        while (true) {
            synchronized (this) {
                if (socket != null) {
                    try {
                        InputStream is = socket.getInputStream();
                        byte[] bytes = new byte[256];
                        int len = is.read(bytes);

                        System.out.println("收到" + getHost(socket) + "信息：" + new String(bytes, 0, len));
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    private static String getHost(Socket socket) {
        return socket.getInetAddress().getHostAddress() + ":" + socket.getPort();
    }
}

UDP

• UDP是一个面向无连接的通信协议，不安全，容易丢包

package com.xiye.single;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.util.Arrays;

/**
 * Create by xiye on 2019/12/6 18:31
 */
public class ServerUDP {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket(1314);
        while (true) {
            byte[] bytes = new byte[256];
            // 获取客户端请求信息
            DatagramPacket packet = new DatagramPacket(bytes, bytes.length);
            socket.receive(packet);         // 阻塞
            System.out.println(new String(packet.getData(), 0, packet.getLength()));

            // 返回信息
            byte[] b = new byte[packet.getLength()];
            System.arraycopy(packet.getData(), 0, b, 0, packet.getLength());

            System.out.println(getHost(packet) + "：" + Arrays.toString(b));

            packet.setData(b);
            socket.send(packet);
        }
    }
    private static String getHost(DatagramPacket packet) {
        return packet.getAddress().getHostAddress() + ":" + packet.getPort();
    }
}

package com.xiye.single;

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

/**
 * Create by xiye on 2019/12/6 18:31
 */
public class ClientUDP {
    public static void main(String[] args) throws IOException {

        for (int i = 0; i < 100; i++) {
            new Thread(() -> {
                try {
                    new ClientUDP();
                    //Thread.sleep(500);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }

    public ClientUDP() throws IOException {
        DatagramSocket socket = new DatagramSocket();
        byte[] bytes = "使用UDP数据包传输".getBytes();

        DatagramPacket packet = new DatagramPacket(bytes, bytes.length, InetAddress.getByName("192.168.31.103"), 1314);
        socket.send(packet);

        // 获取回返信息
        byte[] b = new byte[packet.getLength()];
        DatagramPacket dp = new DatagramPacket(packet.getData(), packet.getLength());
        socket.receive(dp);
        System.out.println("收到" + getHost(dp) + "返回信息：" + new String(dp.getData(), 0, dp.getLength()));
    }

    private static String getHost(DatagramPacket packet) {
        return packet.getAddress().getHostAddress() + ":" + packet.getPort();
    }
}