0基础学java-day21(网络编程)

一、网络的相关概念

1 网络通信

2?网络?

3?ip 地址?

4.ipv4 地址分类?

?5.域名

?

6?网络通信协议?

?

7.网络通信协议?

8.TCP 和 UDP?

?二、InetAddress 类 &Socket

?1 相关方法

package com.hspedu.api;

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

/**
 * @author 林然
 * @version 1.0
 * 演示INetAddress类的使用
 */
public class API_ {
    public static void main(String[] args) throws UnknownHostException {
        //获取本机的INetAddress对象
        InetAddress inetAddress =InetAddress.getLocalHost();
        System.out.println(inetAddress);
        //根据指定的主机名获取 INetAddress对象
        InetAddress host = InetAddress.getByName("Admin-Lin-Ran");
        System.out.println(host);
        //根据一个域名返回InetAddress对象
        InetAddress host2 =InetAddress.getByName("www.baidu.com");
        System.out.println(host2);
        //通过InetAdress对象，获取对应的地址
        String hostAddress =host2.getHostAddress();//
        System.out.println(hostAddress);
        //通过InetAdress对象，获取对应的主机名或者域名
        String hostName =host2.getHostName();//
        System.out.println(hostName);
    }
}

?2 Socket

2.1?基本介绍

?2.2 示意图

三、TCP 网络通信编程?

1.基本介绍

2 应用案例 1(使用字节流)?

?【SreeverSocket对应多个socket】

【Sever】

package com.hspedu.socket;

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

/**
 * @author 林然
 * @version 1.0
 * 服务端
 */
public class SocketTCP01Server {
    public static void main(String[] args) throws IOException {
        //思路
        //1. 在本机 的 9999 端口监听, 等待连接
        // 细节: 要求在本机没有其它服务在监听 9999
        // 细节：这个 ServerSocket 可以通过 accept() 返回多个 Socket[多个客户端连接服务器的并发]
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("服务端，在 9999 端口监听，等待连接..");
        //2. 当没有客户端连接 9999 端口时，程序会 阻塞, 等待连接
        // 如果有客户端连接，则会返回 Socket 对象，程序继续
        Socket socket=serverSocket.accept();
        System.out.println("服务端 socket =" + socket.getClass());
        //3. 通过 socket.getInputStream() 读取客户端写入到数据通道的数据, 显示
        InputStream inputStream = socket.getInputStream();
        //4. IO 读取
        byte[] buf = new byte[1024];
        int readLen = 0;
        while((readLen=inputStream.read(buf))!=-1){
            System.out.println(new String(buf,0,readLen));//根据读取到的实际长度，显示内容
        }
        //5.关闭流和 socket
        inputStream.close();
        socket.close();
        serverSocket.close();


    }
}

【Client】

package com.hspedu.socket;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

/**
 * @author 林然
 * @version 1.0
 * 客户端
 * 发送hello server给服务端
 */
public class SocketTCP01Client {
    public static void main(String[] args) throws IOException {
        //思路
        //1. 连接服务端 (ip , 端口）
        //解读: 连接本机的 9999 端口, 如果连接成功，返回 Socket 对象
        Socket socket = new Socket(InetAddress.getLocalHost(),9999);
        System.out.println("客户端 socket 返回=" + socket.getClass());
        //2. 连接上后，生成 Socket, 通过 socket.getOutputStream()

        // 得到 和 socket 对象关联的输出流对象
        OutputStream outputStream = socket.getOutputStream();
        //3. 通过输出流，写入数据到 数据通道
        outputStream.write("hello,server".getBytes());
        //关闭流对象和socket
        outputStream.close();
        socket.close();
    }
}

3.应用案例 2(使用字节流)

【服务器端】

package com.hspedu.socket;

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

/**
 * @author 林然
 * @version 1.0
 * 服务端
 */
public class SocketTCP02Server {
    public static void main(String[] args) throws IOException {
        //思路
        //1. 在本机 的 9999 端口监听, 等待连接
        // 细节: 要求在本机没有其它服务在监听 9999
        // 细节：这个 ServerSocket 可以通过 accept() 返回多个 Socket[多个客户端连接服务器的并发]
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("服务端，在 9999 端口监听，等待连接..");
        //2. 当没有客户端连接 9999 端口时，程序会 阻塞, 等待连接
        // 如果有客户端连接，则会返回 Socket 对象，程序继续
        Socket socket=serverSocket.accept();
        System.out.println("服务端 socket =" + socket.getClass());
        //3. 通过 socket.getInputStream() 读取客户端写入到数据通道的数据, 显示
        InputStream inputStream = socket.getInputStream();
        //4. IO 读取
        byte[] buf = new byte[1024];
        int readLen = 0;
        while((readLen=inputStream.read(buf))!=-1){
            System.out.println(new String(buf,0,readLen));//根据读取到的实际长度，显示内容
        }
        // 设置结束标记
        socket.shutdownInput();
        OutputStream outputStream = socket.getOutputStream();
        String str ="hello,client";
        outputStream.write(str.getBytes());
        // 设置结束标记
        socket.shutdownOutput();
        //5.关闭流和 socket
        outputStream.close();
        inputStream.close();
        socket.close();
        serverSocket.close();

    }
}

?【客户端】

package com.hspedu.socket;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

/**
 * @author 林然
 * @version 1.0
 * 客户端，发送 "hello, server" 给服务端
 */
public class SocketTCP02Client {
    public static void main(String[] args) throws IOException {
        //思路
        //1. 连接服务端 (ip , 端口）
        //解读: 连接本机的 9999 端口, 如果连接成功，返回 Socket 对象
        Socket socket = new Socket(InetAddress.getLocalHost(),9999);
        System.out.println("客户端 socket 返回=" + socket.getClass());
        //2. 连接上后，生成 Socket, 通过 socket.getOutputStream()

        // 得到 和 socket 对象关联的输出流对象
        OutputStream outputStream = socket.getOutputStream();
        //3. 通过输出流，写入数据到 数据通道
        outputStream.write("hello,server".getBytes());
        // 设置结束标记
        socket.shutdownOutput();
        InputStream inputStream = socket.getInputStream();
        byte [] buf =new byte[1024];
        int readl=0;
        while ((readl=inputStream.read(buf))!=-1){
            System.out.println(new String(buf,0,readl));
        }
        // 设置结束标记
        socket.shutdownInput();
        //关闭流对象和socket
        inputStream.close();
        outputStream.close();
        socket.close();
    }
}

4.应用案例 3(使用字符流)

【Sever】

package com.hspedu.socket;

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

/**
 * @author 林然
 * @version 1.0
 */
public class SocketTCP03Server {
    public static void main(String[] args) throws IOException {
        //思路
        //1. 在本机 的 9999 端口监听, 等待连接
        // 细节: 要求在本机没有其它服务在监听 9999
        // 细节：这个 ServerSocket 可以通过 accept() 返回多个 Socket[多个客户端连接服务器的并发]
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("服务端，在 9999 端口监听，等待连接..");
        //2. 当没有客户端连接 9999 端口时，程序会 阻塞, 等待连接
        // 如果有客户端连接，则会返回 Socket 对象，程序继续
        Socket socket=serverSocket.accept();
        System.out.println("服务端 socket =" + socket.getClass());
        //3. 通过 socket.getInputStream() 读取客户端写入到数据通道的数据, 显示
        InputStream inputStream = socket.getInputStream();
        BufferedReader bufferedReader =new BufferedReader(new InputStreamReader(inputStream));

        //4. IO 读取,使用字符流
        String str1=bufferedReader.readLine();
        System.out.println(str1);
        // 设置结束标记

        OutputStream outputStream = socket.getOutputStream();
        BufferedWriter bufferedWriter =new BufferedWriter(new OutputStreamWriter(outputStream));
        String str ="hello,client";
        bufferedWriter.write(str);
        // 设置结束标记
        bufferedWriter.newLine();
        bufferedWriter.flush();
        //5.关闭流和 socket
        bufferedReader.close();
        bufferedWriter.close();
        
        socket.close();
        serverSocket.close();
    }
}

?【client】

package com.hspedu.socket;

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

/**
 * @author 林然
 * @version 1.0
 */
public class SocketTCP03Client {
    public static void main(String[] args) throws IOException {
        //思路
        //1. 连接服务端 (ip , 端口）
        //解读: 连接本机的 9999 端口, 如果连接成功，返回 Socket 对象
        Socket socket = new Socket(InetAddress.getLocalHost(),9999);
        System.out.println("客户端 socket 返回=" + socket.getClass());
        //2. 连接上后，生成 Socket, 通过 socket.getOutputStream()

        // 得到 和 socket 对象关联的输出流对象
        OutputStream outputStream = socket.getOutputStream();
        //3. 通过输出流，写入数据到 数据通道,要求使用字符流
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
        bufferedWriter.write("hello,server 字符流");

        bufferedWriter.newLine();//插入一个换行符，表示输入结束，注意要求对方用realLine()！！！
        //如果使用的字符流，需要手动刷新，否则数据不会写入数据通道
        bufferedWriter.flush();

        InputStream inputStream = socket.getInputStream();
        BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream));
        String str =bufferedReader.readLine();
        System.out.println(str);
        // 设置结束标记

        //关闭流对象和socket
        bufferedReader.close();
        bufferedWriter.close();

        socket.close();
    }
}

5.应用案例 4【传送文件】

?【StreamUtils】

package com.hspedu.upload;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

/**
 * 此类用于演示关于流的读写方法
 *
 */
public class StreamUtils {
	/**
	 * 功能：将输入流转换成byte[]， 即可以把文件的内容读入到byte[]
	 * @param is
	 * @return
	 * @throws Exception
	 */
	public static byte[] streamToByteArray(InputStream is) throws Exception{
		ByteArrayOutputStream bos = new ByteArrayOutputStream();//创建输出流对象
		byte[] b = new byte[1024];//字节数组
		int len;
		while((len=is.read(b))!=-1){//循环读取
			bos.write(b, 0, len);//把读取到的数据，写入bos	
		}
		byte[] array = bos.toByteArray();//然后将bos 转成字节数组
		bos.close();
		return array;
	}
	/**
	 * 功能：将InputStream转换成String
	 * @param is
	 * @return
	 * @throws Exception
	 */
	
	public static String streamToString(InputStream is) throws Exception{
		BufferedReader reader = new BufferedReader(new InputStreamReader(is));
		StringBuilder builder= new StringBuilder();
		String line;
		while((line=reader.readLine())!=null){
			builder.append(line+"\r\n");
		}
		return builder.toString();
		
	}

}

【服务端】

package com.hspedu.upload;

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

/**
 * @author 林然
 * @version 1.0
 * 文件上传的服务器
 */
public class TCPFileUploadServer {
    public static void main(String[] args) throws Exception {
        //1.服务端在本机监听8888端口
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("服务端在8888端口监听");
        //2等待连接
        Socket socket = serverSocket.accept();
        //3 读取客户端发送的数据
        //通过Socket得到输入流
        InputStream inputStream =socket.getInputStream();
        BufferedInputStream bufferedInputStream =new BufferedInputStream(inputStream);
        byte[] bytes =StreamUtils.streamToByteArray(bufferedInputStream);
        BufferedOutputStream bufferedOutputStream =new BufferedOutputStream
                (new FileOutputStream("src\\jmq.jpg"));
        bufferedOutputStream.write(bytes);
        bufferedOutputStream.close();

        //向客户端回复收到图片
        //通过socket获取到输出流[字符]
        BufferedWriter bufferedWriter =new BufferedWriter
                (new OutputStreamWriter(socket.getOutputStream()));
        bufferedWriter.write("服务端收到图片");
        bufferedWriter.flush();//把内容刷新

        //设置结束标记
        socket.shutdownOutput();


        //关闭其他资源
        bufferedWriter.close();
        bufferedInputStream.close();
        socket.close();
        serverSocket.close();
    }
}

【客户端】

package com.hspedu.upload;

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

/**
 * @author 林然
 * @version 1.0
 * 文件上传的客户端
 */
public class TCPFileUploadClient {
    public static void main(String[] args) throws Exception {
        //客户端连接服务端 8888端口得到Socket对象
        Socket socket=new Socket(InetAddress.getLocalHost(),8888);
        //创建读取磁盘文件的输入流
        String filePath="e:\\jmq.jpg";
        BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(filePath));
        //bytes就是filePath对应的字节数组
        byte[] bytes= StreamUtils.streamToByteArray(bufferedInputStream);
        //通过Socket获取到输出流，将bytes数据发送给服务端
        OutputStream outputStream =socket.getOutputStream();
        BufferedOutputStream bufferedOutputStream =new BufferedOutputStream(outputStream);
        bufferedOutputStream.write(bytes);//将文件写入到数据通道
        //关闭流
       bufferedInputStream.close();
        socket.shutdownOutput();

        //设置一个结束的标志
        //接收服务端的信息
        InputStream inputStream=socket.getInputStream();
        String message=StreamUtils.streamToString(inputStream);
        System.out.println(message);

        socket.shutdownInput();


        //关闭相关流

        inputStream.close();
      bufferedOutputStream.close();
        socket.close();
    }
}

6.netstat 指令

7.TCP 网络通讯不为人知的秘密?

四、UDP 网络通信编程[了解]?

1 基本介绍

2 基本流程?

?3.应用案例

A端口

package com.hspedu.udp;

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

/**
 * @author 林然
 * @version 1.0
 * UDP 接收端
 */
public class UDPReceiverA {
    public static void main(String[] args) throws IOException {
        //1.创建一个DatagramSocket 对象，准备接受数据
        DatagramSocket datagramSocket = new DatagramSocket(9999);
        //2.构建一个DatagramPacket准备接受数据
        //udp一个数据包大小限制在64K，不适用传递大量数据
        byte [] buf =new byte[64*1024];
        DatagramPacket datagramPacket = new DatagramPacket(buf, buf.length);
        //3.调用接收方法
        //填充到packet对象
        //提示: 当有数据包发送到 本机的 9999 端口时，就会接收到数据
        // 如果没有数据包发送到 本机的 9999 端口, 就会阻塞等待
        System.out.println("接收端 A 等待接收数据..");
        datagramSocket.receive(datagramPacket);
        //4 拆包
        int length= datagramPacket.getLength();//实际接收到的数据字节长度
        byte [] data =datagramPacket.getData();
        String s = new String(data, 0, length);
        System.out.println(s);
        String message="好的，收到";
        DatagramPacket datagramPacket1 =new DatagramPacket(message.getBytes(),message.getBytes().length, InetAddress.getLocalHost(),9998);
        datagramSocket.send(datagramPacket1);
        //关闭
        datagramSocket.close();
        System.out.println("A端退出");
    }
}

?B端口

package com.hspedu.udp;

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

/**
 * @author 林然
 * @version 1.0
 * 发送端 B ====> 也可以接收数据
 */
public class UDPSenderB {
    public static void main(String[] args) throws IOException {
        //1.创建 DatagramSocket 对象，准备在 9998 端口 接收数据
        DatagramSocket datagramSocket =new DatagramSocket(9998);
        //2 将需要发送的数据封装到Datagrampacket对象
        byte[] bytes = "hello,明天吃火锅".getBytes();
        //说明: 封装的 DatagramPacket 对象 bytes 内容字节数组 , bytes.length , 主机(IP) , 端口
        DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length, InetAddress.getLocalHost(), 9999);
        datagramSocket.send(datagramPacket);
        //3.=== 接收从 A 端回复的信息
//(1) 构建一个 DatagramPacket 对象，准备接收数据
        // 在前面讲解 UDP 协议时，老师说过一个数据包最大 64k
        byte [] buf=new byte[1024*64];
        DatagramPacket datagramPacket1=new DatagramPacket(buf,buf.length);
        // 如果没有数据包发送到 本机的 9998 端口, 就会阻塞等待.
        datagramSocket.receive(datagramPacket1);
        int length =datagramPacket1.getLength();
        byte [] data=datagramPacket1.getData();
        System.out.println(new String(data,0,length));
        //关闭资源
        datagramSocket.close();
        System.out.println("B端退出");
    }
}

五、本章作业

1.作业一?

【服务端】

package com.hspedu.homework;

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

/**
 * @author 林然
 * @version 1.0
 */
public class homework01_service {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket =new ServerSocket(9999);
        System.out.println("服务器端口等待连接");
        Socket socket =serverSocket.accept();

        //接受数据
        InputStream inputStream =socket.getInputStream();
        BufferedReader bufferedReader =new BufferedReader(new InputStreamReader(inputStream));
        String str=bufferedReader.readLine();
        System.out.println(str);
        String message="";
        if(str.equals("name")){
            message="Linran";
        }else if(str.equals("hobby")){
            message="java编程";
        }else {
            message="你说啥呢";
        }

        OutputStream outputStream=socket.getOutputStream();
        BufferedWriter bufferedWriter =new BufferedWriter(new OutputStreamWriter(outputStream));
        bufferedWriter.write(message,0,message.length());
        bufferedWriter.flush();
        socket.shutdownOutput();

        //关闭流
        bufferedWriter.close();
        bufferedReader.close();
        socket.close();
        serverSocket.close();
    }
}

?【客户端】

package com.hspedu.homework;

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

/**
 * @author 林然
 * @version 1.0
 */
public class homework01_client {
    public static void main(String[] args) throws IOException {
        //建立连接
        Socket socket=new Socket(InetAddress.getLocalHost(),9999);
        Scanner scanner=new Scanner(System.in);
        //用户输入
        String message =scanner.next();
        //获取输出流
        OutputStream outputStream =socket.getOutputStream();
        BufferedWriter bufferedWriter =new BufferedWriter(new OutputStreamWriter(outputStream));
        bufferedWriter.write(message,0,message.length());
        bufferedWriter.flush();
        socket.shutdownOutput();

        //发送等待回复
        InputStream inputStream =socket.getInputStream();
        BufferedReader bufferedReader =new BufferedReader(new InputStreamReader(inputStream));
        String data =bufferedReader.readLine();
        System.out.println(data);

        //关闭流
        bufferedReader.close();
        bufferedWriter.close();
        socket.close();


    }
}

2.作业二

【接收端】

package com.hspedu.homework;

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

/**
 * @author 林然
 * @version 1.0
 */
public class homework02_A_receive {
    public static void main(String[] args) throws IOException {
        DatagramSocket datagramSocket =new DatagramSocket(9999);
        byte [] buf =new byte[1024*64];
        DatagramPacket datagramPacket=new DatagramPacket(buf,buf.length);
        System.out.println("等待；连接");
        datagramSocket.receive(datagramPacket);
        int length =datagramPacket.getLength();
        byte [] data =datagramPacket.getData();
        String message =new String(data,0,length);//注意这里第三个参数不要用data.length
        System.out.println(message);
        String answer =" ";
        if("四大名著是哪些".equals(message)){
            answer="四大名著是<红楼梦>........";
        }
        else {
            answer="What?";
        }
        System.out.println(answer);
        DatagramPacket datagramPacket1 =new DatagramPacket(answer.getBytes(),answer.getBytes().length, InetAddress.getLocalHost(),9998);
        datagramSocket.send(datagramPacket1);

        //关闭流
        datagramSocket.close();
    }
}

?【发送端】

package com.hspedu.homework;

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

/**
 * @author 林然
 * @version 1.0
 */
public class homework02_B_send {
    public static void main(String[] args) throws IOException {
        //建立我方监听端口
        DatagramSocket datagramSocket =new DatagramSocket(9998);
        //等待用户输入
        Scanner scanner =new Scanner(System.in);
        String message=scanner.next();
        //封装
        DatagramPacket datagramPacket =new DatagramPacket(message.getBytes(),message.getBytes().length, InetAddress.getLocalHost(),9999);
        //发送
        datagramSocket.send(datagramPacket);
        //获取回复信息
        byte [] buf =new byte[1024*64];
        DatagramPacket datagramPacket1 =new DatagramPacket(buf,buf.length);
        datagramSocket.receive(datagramPacket1);
        int length =datagramPacket1.getLength();
        byte [] data =datagramPacket1.getData();
        String answer =new String(data,0,length);
        System.out.println(answer);
        //关闭流
        datagramSocket.close();

    }
}

3.作业三

【服务器端】

package com.hspedu.homework;

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

/**
 * @author 林然
 * @version 1.0
 */
public class homework03_server {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket=new ServerSocket(9999);
        System.out.println("等待连接");
        Socket socket =serverSocket.accept();
        //获取数据
        InputStream inputStream =socket.getInputStream();
        //利用工具类
        String filename=StreamUtils.streamToString(inputStream);
        System.out.println("客户希望下载的文件名"+filename);
        //判断是否存在
        String filename1="src\\"+filename;
        File file =new File(filename1);
        System.out.println("客户希望下载的文件名"+filename1);
        String send_filepath =filename1;
        if(!file.exists()){
            send_filepath="src\\无名.mp3";
        }

        BufferedInputStream bufferedInputStream=new BufferedInputStream(new FileInputStream(send_filepath));
        //利用工具类
        byte [] bytes=StreamUtils.streamToByteArray(bufferedInputStream);

        //输出
        BufferedOutputStream bufferedOutputStream =new BufferedOutputStream(socket.getOutputStream());
        bufferedOutputStream.write(bytes);
        bufferedOutputStream.flush();
        socket.shutdownOutput();
        //关闭流
        bufferedOutputStream.close();
        bufferedInputStream.close();
        socket.close();
        serverSocket.close();





    }
}

【客户端】

package com.hspedu.homework;

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

/**
 * @author 林然
 * @version 1.0
 */
public class homework03_client {
    public static void main(String[] args) throws Exception {
        Scanner scanner =new Scanner(System.in);
        //用户输入
        System.out.println("请输入你要查找的文件名");
        String filename=scanner.next();
        //建立连接
        Socket socket =new Socket(InetAddress.getLocalHost(),9999);


        OutputStream outputStream =socket.getOutputStream();
        BufferedWriter bufferedWriter =new BufferedWriter(new OutputStreamWriter(outputStream));
        //写入
        bufferedWriter.write(filename);
        bufferedWriter.flush();
        socket.shutdownOutput();
        //获取回复
        InputStream inputStream =socket.getInputStream();
        BufferedInputStream bufferedInputStream =new BufferedInputStream(inputStream);
        byte [] data =StreamUtils.streamToByteArray(bufferedInputStream);
        String dest_path ="e:\\"+filename;
        File file =new File(dest_path);
        BufferedOutputStream bufferedOutputStream =new BufferedOutputStream(new FileOutputStream(file));
        bufferedOutputStream.write(data);
        bufferedOutputStream.flush();
        //关闭流
        bufferedOutputStream.close();
        bufferedInputStream.close();
        bufferedWriter.close();
        socket.close();

    }
}

【工具类】

package com.hspedu.homework;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;

/**
 * 此类用于演示关于流的读写方法
 *
 */
public class StreamUtils {
	/**
	 * 功能：将输入流转换成byte[]， 即可以把文件的内容读入到byte[]
	 * @param is
	 * @return
	 * @throws Exception
	 */
	public static byte[] streamToByteArray(InputStream is) throws Exception{
		ByteArrayOutputStream bos = new ByteArrayOutputStream();//创建输出流对象
		byte[] b = new byte[1024];//字节数组
		int len;
		while((len=is.read(b))!=-1){//循环读取
			bos.write(b, 0, len);//把读取到的数据，写入bos	
		}
		byte[] array = bos.toByteArray();//然后将bos 转成字节数组
		bos.close();
		return array;
	}
	/**
	 * 功能：将InputStream转换成String
	 * @param is
	 * @return
	 * @throws Exception
	 */
	
	public static String streamToString(InputStream is) throws Exception{
		BufferedReader reader = new BufferedReader(new InputStreamReader(is));
		StringBuilder builder= new StringBuilder();
		String line;
		while((line=reader.readLine())!=null){
			builder.append(line+"\r\n");
		}
		return builder.toString();
		
	}

}