Can't send file from server to client over LAN

问题

Here is a code snippet of both server side and client side through which a user can request a file from server. The server will send the file.

There's two problems:

• Server side sends empty file.
• When trying to run the code in Local area network it is giving ioexception

I don't understand why sever is sending empty file, please help.

SERVER SIDE CODE :

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
 package ftpserverclient.FileClientServer;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

/**
 *
 * @author Arnab
 */
public class FileServer {

public static void main(String args[])throws IOException
         { 
             ServerSocket ss=null;
             try
             {  
                 ss=new ServerSocket(8085);
             }
             catch(IOException e)
             { 
                 System.out.println("couldn't listen");
                 System.exit(0);
             }
             Socket cs=null;
             try
             { 
                 cs=ss.accept();
                 System.out.println("Connection established"+cs);
             }
             catch(Exception e)
             { 
                 System.out.println("Accept failed");
                 System.exit(1);
             } 
             PrintWriter put=new PrintWriter(cs.getOutputStream(),true);
             BufferedReader st=new BufferedReader(new InputStreamReader(cs.getInputStream()));
             String s=st.readLine();


             String path = s ; 
             System.out.println("The requested file is path: "+path);
             System.out.println("The requested file is : "+s);
             File f=new File(path);
             if(f.isFile())
             { 
                 BufferedReader d=new BufferedReader(new FileReader(f));
                 String line;
                 while((line=d.readLine())!=null)
                 {
                     put.write(line);
                     put.flush();
                 }
                 d.close();
                 System.out.println("File transfered");
                 cs.close();
                 ss.close();
             } 
         }

}

CLIENT SIDE CODE :

package ftpserverclient.FileClientServer;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

/**
 *
 * @author Arnab
 */
public class FileClient {

public static void main(String srgs[])throws IOException
{
    Socket s=null;
    BufferedReader get=null;
    PrintWriter put=null;
    try
    { 
        s=new Socket("127.0.0.1",8085);
        get=new BufferedReader(new InputStreamReader(s.getInputStream()));
        put=new PrintWriter(s.getOutputStream(),true);

        String u,f;
        System.out.println("Enter the file name to transfer from server:");
        DataInputStream dis=new DataInputStream(System.in);
        f=dis.readLine();
        put.println(f);

        File f1=new File(f);



        FileOutputStream  fs=new FileOutputStream(new File("C:\\PictureDestination\\a.jpg"));


        while((u=get.readLine())!=null)
        { 
            System.out.println(u);
            byte jj[]=u.getBytes();
            fs.write(jj);
        } 
        fs.close();
        System.out.println("File received");
        s.close();
    }catch(Exception e)
    {
        e.printStackTrace();
        System.exit(0);
    }
}       

}

回答1:

At client side , you forgot to write put.fflush(); after put.println(f); while sending file name to server.

回答2:

Finally i found this this thing working .

here are the changes.

changing String u,f; to String f; int u; and while((u=get.readLine())!=null) { System.out.println(u); byte jj[]=u.getBytes(); fs.write(jj); } into while((u=get.read(jj,0,1024))!=-1) { fs.write(jj,0,u); } fs.close();

but 1 problem still exists. It is not working ON LAN.

来源：https://stackoverflow.com/questions/21349796/cant-send-file-from-server-to-client-over-lan