Java 发送字符串(文件名)和文件通过同一套接字

Question

我会通过套接字发送"文件名"和"文件"，我能够轻松发送文件，但是当我尝试发送字符串例如PrintWriter pw.println（）或DataOutputStream或" out.writeUTF （ ）"文件发送损坏时，我在StackOverflow上阅读了很多问题但没有找到答案，我正在寻找一些发送字符串和文件的例子， 你能帮忙吗？

服务器

package serverprova;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

public class ServerProva {
final static int porta=8888;//porta server dove si collegano i client
public static void main(String[] args) throws IOException {
    // TODO code application logic here
    ServerSocket serverSocket=null;
    boolean ascoltando=true;
    serverSocket = new ServerSocket(porta);//avvia il server con il  numero di porta
    Socket s;
    BufferedReader br1=null;
     // ******  interfaccia f=new interfaccia);
      boolean r=true;
      BufferedInputStream bis=null;
       Scanner sc;
    FileOutputStream fout;
    while(ascoltando)
        {
        s=serverSocket.accept();// this socket 
    String filename="";
    String nome_cartella="";
    InputStream in = null;
OutputStream out = null;
   DataInputStream inString;

        inString = new DataInputStream(new BufferedInputStream(s.getInputStream()));
       //  filename = inString.readUTF();
       //  nome_cartella = inString.readUTF();

    in = s.getInputStream();

    //out = new FileOutputStream(nome_cartella+"/"+filename);
out = new FileOutputStream("ciao"+"/"+"asd.jpg");
byte[] b = new byte[20*1024];
int i ;

        while((i = in.read(b)) >0){
            out.write(b, 0, i);
        }
        out.close();
in.close();
//inString.close();
s.close();
        }

 }
}

客户

    package clientprova;

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

public class ClientProva {
final static int porta=8888;
public static void main(String[] args) throws FileNotFoundException, IOException {
    File file;
    file = new File("kirlian12.jpg");
   InetAddress host = InetAddress.getLocalHost();
Socket sock = new Socket(host.getHostName(), 8888);
   DataOutputStream outString = new DataOutputStream(new BufferedOutputStream(sock.getOutputStream()));
     //   outString.writeUTF(file.getName());
      //  outString.writeUTF("rivelatore2");
     //   outString.flush();
     byte[] b = new byte[20*1024]; 

                InputStream in = new FileInputStream(file);
        OutputStream out = sock.getOutputStream();
        int i ;
        while ((i = in.read(b)) >0    ) {
            out.write( b , 0 , i);
        }

        out.close();
        in.close();
sock.close();

   }

 }

当我尝试取消注释注释的行时，我的文件已损坏

Answer 1

当你用 BufferedInputStream 包装 InputStream 时，后者"拥有"InputStream。这意味着当您调用 readUtf() 时，BufferedInputStream 从 InputStream 读取的字节数可能会超过读取 UTF 字符串所需的字节数。因此，当您下次直接访问 InputStream 时，传输文件的某些部分丢失了（因为它以前被读入 BufferedInputStream 的缓冲区并且当前驻留在那里）。

inString = new DataInputStream(new BufferedInputStream(s.getInputStream()));
filename = inString.readUTF();
nome_cartella = inString.readUTF();
...
in = s.getInputStream();
while((i = in.read(b)) >0){

您必须从两个备选方案中进行选择：要么始终使用原始输入流，要么始终使用 BufferedInputStream。同样的推理也适用于输出流（但您设法通过调用 flush() 来避免问题）。