File transfer from Client to Server side

[Srivatsa Sri]

Hello , I am new to coderanch. Please guide me with the following problem. I have Server and Client java files. Client sends a file to Server, Server receives it and saves in the present working directory of Server java file. How to change the target directory in Server from current working directory? Here is my code :

Server.java

import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server extends Thread {
    public static final int PORT = 3332;
    public static final int BUFFER_SIZE = 100;

    @Override
    public void run() {
        try {
            ServerSocket serverSocket = new ServerSocket(PORT);

            while (true) {
                Socket s = serverSocket.accept();
                saveFile(s);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void saveFile(Socket socket) throws Exception {
        ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
        ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
        FileOutputStream fos = null;
        byte [] buffer = new byte[BUFFER_SIZE];

        // 1. Read file name.
        Object o = ois.readObject();

        if (o instanceof String) {
            fos = new FileOutputStream(o.toString());
        } else {
            throwException("Something is wrong");
        }

        // 2. Read file to the end.
        Integer bytesRead = 0;

        do {
            o = ois.readObject();

            if (!(o instanceof Integer)) {
                throwException("Something is wrong");
            }

            bytesRead = (Integer)o;

            o = ois.readObject();

            if (!(o instanceof byte[])) {
                throwException("Something is wrong");
            }

            buffer = (byte[])o;

            // 3. Write data to output file.
            fos.write(buffer, 0, bytesRead);
          
        } while (bytesRead == BUFFER_SIZE);
        
        System.out.println("File transfer success");
        
        fos.close();

        ois.close();
        oos.close();
    }

    public static void throwException(String message) throws Exception {
        throw new Exception(message);
    }

    public static void main(String[] args) {
        new Server().start();
    }
}  

Client.java

import java.io.File;
import java.io.FileInputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.util.Arrays;
import java.lang.*;
import java.util.Scanner;


public class Client {
    public static void main(String[] args) throws Exception {
        String fileName = null;

       try {
            fileName = args[0];
        } catch (Exception e) {
        System.out.println("Enter the name of the file :");
        Scanner scanner = new Scanner(System.in);
        String file_name = scanner.nextLine();
         
        File file = new File(file_name);
        Socket socket = new Socket("localhost", 3332);
        ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
        ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());

        oos.writeObject(file.getName());

        FileInputStream fis = new FileInputStream(file);
        byte [] buffer = new byte[Server.BUFFER_SIZE];
        Integer bytesRead = 0;

        while ((bytesRead = fis.read(buffer)) > 0) {
            oos.writeObject(bytesRead);
            oos.writeObject(Arrays.copyOf(buffer, buffer.length));
        }

        oos.close();
        ois.close();
        System.exit(0);    
}

}

}  

[Daniel Georgescu]

I just replaced the line

fos = new FileOutputStream(o.toString());   

with

fos = new FileOutputStream(new File("D:\\temp\\test123.txt")); 

in Server.java file and it worked for me.

[Srivatsa Sri]

Hi Daniel,

Thank you for the response. You are right when we upload the one file or the file we know already. But here its dynamic, Client enters the name of the file_path and this file has to be saved in a directory predefined in Server for example :

fos = new FileOutputStream(new File(/home/name/Server/name_of_the_file));

As of now, the file sent by Client will be saved under the current working directory where Server.java is placed.

Hope you got my point...Verify it. Thanks again.

[Jayesh A Lalwani]

You should do something like this

FileOutputStream fos = new FileOutputStream(new File (targetDirectory, fileName));

Here targetDirectory is the full path of folder in which you want to save the file. It will be better if you get the target directory from a configuration item rather than hard coding it. It will make your code more portable.

[Srivatsa Sri]

Yes, yeah thats what I need , Jayesh. Thanks for the suggestion. Can you please put it to code ? I tried but, the data is not transferring , only file is transferred with 0KB memory size.

Modified it like this :

if (o instanceof String) {
            File dir = new File("/home/user/");
            fos = new FileOutputStream(o.toString());
            location = new FileOutputStream(new File(dir,o.toString()));
            
        } 

[Jayesh A Lalwani]

Now, you are creating 2 files; one in the same place where you were creating before, one in the place where you want to create. Which FileOutputStream are you writing your bytes to? If you write to fos, and not to location, then the file that location points to will have 0 bytes, and the file that fos points to will have all the bytes

BTW, if you want to create the file in the user's home directory, it's better to use "user.home" system property rather than hardcoding the path in your code