使用TCP进行文件传输时，客户端到服务端无法使用bufferedOutputStream

Question

在发送端，如果我用outputStream传输到服务端是可以的，但是如果用bufferedoutputstream，在服务端就接受不到数据，连接什么都正常。。

发送端数据如下
package com.itheima.javaSE.Internet;

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

public class TCPsend {
public static void main(String[] args) throws IOException {
faild();
}

private static void faild() throws IOException {
    //本地的流，将数据写到内存
    BufferedInputStream bis = new BufferedInputStream(new FileInputStream("C:\\Users\\86130\\Desktop\\新建文件夹\\a.txt"));
    //网络的流，将数据写到网络
    Socket socket = new Socket("127.0.0.1", 10002);
    OutputStream os = socket.getOutputStream();
    BufferedOutputStream bos = new BufferedOutputStream(os);
    //读取和写入操作
    byte[] bytes = new byte[1024];
    int len;
    while ((len = bis.read(bytes)) != -1) {
        System.out.println(bytes);
        bos.write(bytes, 0, len);
    }
    //给服务器一个结束标记
    socket.shutdownOutput();
    //接收服务器的数据
    BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
    socket.close();
    bis.close();
}

}

接收端代码如下
public class TCPreceive {
public static void main(String[] args) throws IOException {
faild();
}

private static void faild() throws IOException {
    ServerSocket ss = new ServerSocket(10002);

    Socket accept = ss.accept();
    //网络中的流
    BufferedInputStream bis = new BufferedInputStream(accept.getInputStream());
    //本地的流
    BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("C:\\Users\\86130\\Desktop\\新建文件夹\\b.txt"));
    byte[] bytes = new byte[1024];
    int len;
    while ((len = bis.read(bytes)) != -1) {
        bos.write(bytes, 0, len);
    }
    //回信
    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(accept.getOutputStream()));
    bw.write("下载完毕！");
    bw.newLine();
    bw.flush();

    accept.close();
    ss.close();
    bos.close();
}

}
更改后的发送端数据如下(服务端能接受数据)
package com.itheima.javaSE.Internet;

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

public class TCPsend {
public static void main(String[] args) throws IOException {
faild();
}

private static void faild() throws IOException {
    //本地的流，将数据写到内存
    BufferedInputStream bis = new BufferedInputStream(new FileInputStream("C:\\Users\\86130\\Desktop\\新建文件夹\\a.txt"));
    //网络的流，将数据写到网络
    Socket socket = new Socket("127.0.0.1", 10002);
    OutputStream os = socket.getOutputStream();
    //读取和写入操作
    byte[] bytes = new byte[1024];
    int len;
    while ((len = bis.read(bytes)) != -1) {
        System.out.println(bytes);
        os.write(bytes, 0, len);
    }
    //给服务器一个结束标记
    socket.shutdownOutput();
    //接收服务器的数据
    BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
    socket.close();
    bis.close();
}

}

Answer 1

猜测是写入BufferedOutputStream的数据应缓存空间没有被填充满所以还在缓存中所以需要flush()把数据刷出来