getLockHost//获取本机InetAddress对象
getByName//根据指定主机名/域名获取ip地址对象
getHostName//获取InetAddress对象主机名
getHostAddress//获取InetAddress对象的地址

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

/**
 * @author 一个凡人
 * @version 1.0
 * 服务端
 */
public class Homework03Server {
    public static void main(String[] args) throws IOException {
        //1. 创建端口等待连接
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("服务端等待连接....");
        //2. 创建Socket对象 如果被连接就返回 Socket对象
        Socket socket = serverSocket.accept();
        //3. 接收客户端的内容
        //   这里采用字符流的方式接收
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String line = br.readLine();
        //4. 如果客户端发送的内容是 坦克大战背景音乐 就发送tk.mp3给客户端
        //   否则返回默认音乐 7301.mp3
        String filePath;//定义文件路径
        if ("坦克大战背景".equals(line)) {
            filePath = "j:\\tk.mp3";
        } else {
            filePath = "j:\\7301.mp3";
        }
        //  读取文件
        //  给客户端发送音乐 采用字节流
        OutputStream outputStream = socket.getOutputStream();
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(filePath));
        byte[] buf = new byte[1024];
        int len = 0;
        //一边读一边发送
        while((len = bis.read(buf)) != -1) {
            outputStream.write(buf,0,len);
        }
        //设置结束标记
        socket.shutdownOutput();
        //关闭资源
        socket.close();
        outputStream.close();
        bis.close();
        br.close();
        serverSocket.close();
        System.out.println("服务端退出...");
    }
}

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.util.Scanner;


/**
 * @author 一个凡人
 * @version 1.0
 * 客户端
 */
public class Homework03Client {
    public static void main(String[] args) throws IOException {
        //1. 连接端口
        Socket socket = new Socket(InetAddress.getLocalHost(), 9999);
        
        //2. 给服务端发送需要下载的音乐名 采用Scanner
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入需要下载的音乐名：");
        String musicName = scanner.next();
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
        bw.write(musicName);
        bw.flush();//刷新
        socket.shutdownOutput();//结束标记
        
        //3. 接收服务端发送的文件 并保存到 e:\\
        String destPath = "e:\\" + musicName + ".mp3";
        BufferedOutputStream bos = 
            new BufferedOutputStream(new FileOutputStream(destPath));
        InputStream inputStream = socket.getInputStream();
        byte[] data = new byte[1024];
        int len = 0;
        //循环读取
        while((len = inputStream.read(data)) != -1) {
            bos.write(data,0,len);
            bos.flush();
        }
        //关闭资源
        bos.close();
        inputStream.close();
        bw.close();
        socket.close();
        System.out.println("客户端退出....");
    }
}

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

/**
 * @author 一个凡人
 * @version 1.0
 * 发送端  ---->也可以接收数据
 */
public class UDPSendB {
    public static void main(String[] args) throws IOException {
        //1. 创建 DatagramSocket对象 接收和发送数据
        DatagramSocket socket = new DatagramSocket(9998);

        //2. 将需要发送的数据，封装到 DatagramPacket对象
        byte[] data = "hello,明天去吃火锅...".getBytes();
        // 说明：封装的DatagramPacket 对象data 内容字节数组, data.length, 主机(ip), 端口
        DatagramPacket packet =
                new DatagramPacket(data, 0, data.length, InetAddress.getByName("192.168.42.96"), 9999);
        socket.send(packet);

        //3. 接收
        byte[] buf = new byte[1024];
        DatagramPacket packet1 = new DatagramPacket(buf, buf.length);
        socket.receive(packet1);

        //拆包显示内容
        int length = packet1.getLength();
        byte[] data1 = packet1.getData();
        String s = new String(data1, 0, length);
        System.out.println(s);

        //关闭资源
        socket.close();
        System.out.println("B端退出...");
    }
}

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


/**
 * @author 一个凡人
 * @version 1.0
 * 接收端
 */
public class UDPReceiveA {
    public static void main(String[] args) throws IOException {
        //1. 创建一个 DatagramSocket 对象 准备在9999接收数据
        DatagramSocket socket = new DatagramSocket(9999);
        //2. 创建一个 DatagramPacket 对象 准备接收数据
        //   UDP协议一个数据包最大64k
        byte[] buf = new byte[64 * 1024];
        DatagramPacket packet = new DatagramPacket(buf,  buf.length);
        //3. 调用方法 将通过网络传输的 DatagramPacket对象
        //   注意：当有数据包发送到9999端口时，就会接收到数据
        //         如果没有数据包发送，就会阻塞
        System.out.println("接收端A 等待接收数据...");
        socket.receive(packet);

        //4. 把packet拆包 取出数据并显示
        int length = packet.getLength();//实际接收到的数据字节长度
        byte[] data = packet.getData();//接收到的数据
        String s = new String(data, 0, length);
        System.out.println(s);

        //5. 发送“好的，明天见”
        byte[] data1 = "好的，明天见...".getBytes();
        DatagramPacket packet1 =
                new DatagramPacket(data1, 0, data1.length, InetAddress.getByName("192.168.42.96"), 9998);

        socket.send(packet1);

        //关闭资源
        socket.close();
        System.out.println("A端退出...");
    }
}