Send a file across the network

[dushantha Rathnayake]

Hi,

I have an client server application. in some cases I want to send files between server and client. But I don't know how to do it. Can I do it using socket programming? the files that I want to send can be documents, media files, text files, pdf files, ect.... . Actually I want to send a file across the network. please help me.

thank you.

[Richard Golebiowski]

You could send it using FTP.

[Lester Burnham]

Sockets would work, and might be the fastest way to getting this implemented if the requirements are simple. Or you could use an embedded Java FTP server like http://mina.apache.org/ftpserver/ and a client like http://commons.apache.org/net/

[dushantha Rathnayake]

Hi,

My application is not a web application. I need to implement this file sending on a LAN. If I can use socket programming to do this, then how can I do it? If you have an example code please post it or if you can give me a link please post them. I am new for this socket programming side. Please help me.

Thank you.

[Lester Burnham]

Searching for "java socket tutorial" should find the relevant chapter of the Sun Java Tutorial. It contains an example of a pair of standalone client/server applications that communicate via sockets.

[Richard Golebiowski]

dushantha Rathnayake wrote:Hi,

My application is not a web application. I need to implement this file sending on a LAN. If I can use socket programming to do this, then how can I do it? If you have an example code please post it or if you can give me a link please post them. I am new for this socket programming side. Please help me.

Thank you.

It doesn't matter if it's a web application. As long as the network is TCP, you can use a FTP server and client as was suggested. For a project, I wrote a DOS FTP server in Java and a DOS client in Pascal that was used to replace file transfer vis modem in an application. The client was not a web application.

[Andrey Kozhanov]

Hi!

Below is a very basic sample of using sockets for transfering files of any type over the network, but it could give you general idea. Output file is written to current server working directory and no additional checking is provided. So if file of the same name already exists, it would be overwritten.

Server.java

package transfer;

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 = 3333;
    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);

        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();
    }
}  

and Client.java

package transfer;

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

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

        try {
            fileName = args[0];
        } catch (Exception e) {
            System.out.println("Pass file name as command line argument");
        }

        File file = new File(fileName);
        Socket socket = new Socket("localhost", Server.PORT);
        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();
    }
}