Transfer the File “Client Socket to Server Socket” in Java

Prerequisites:

• Socket Programming in Java
• File Handling in Java

This article describes a one-way client and Server Setup where a client connects, and sends the file to the server and the server writes the file in another location with a different name. It means we send the file using the server socket.

Socket Programming in Java

Socket Programming is used for communicating different JRE in the different networks in java. In simple words, we can say socket programming is connecting two nodes in different networks and communicating two each other.

File Transfer Implementation in Java Socket

In this example, we will create client.java class in this class we make the Socket object and define the server socket port number for communication. In this class, we select which file send over the network.

Client

• To connect to another machine we need two pieces of information first one is the IP address and the second one is the port number.
• In our case, we are using localhost and the port is 900
• We make a Socket object using the java.net package 

Example

Socket ob = new Socket(ip,port _ number)

Now we call the “sendFile” method with the parameter of a file path and we open the file and send the file to the server socket using DataOutputStream Class

Java

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

public class Client {
    private static DataOutputStream dataOutputStream = null;
    private static DataInputStream dataInputStream = null;

    public static void main(String[] args)
    {
        // Create Client Socket connect to port 900
        try (Socket socket = new Socket("localhost", 900)) {

          dataInputStream = new DataInputStream(
                socket.getInputStream());
            dataOutputStream = new DataOutputStream(
                socket.getOutputStream());
            System.out.println(
                "Sending the File to the Server");
          // Call SendFile Method
          sendFile(
                "/home/dachman/Desktop/Program/gfg/JAVA_Program/File Transfer/txt.pdf");

            dataInputStream.close();
            dataInputStream.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }

    // sendFile function define here
    private static void sendFile(String path)
        throws Exception
    {
        int bytes = 0;
        // Open the File where he located in your pc
        File file = new File(path);
        FileInputStream fileInputStream
            = new FileInputStream(file);

        // Here we send the File to Server
        dataOutputStream.writeLong(file.length());
        // Here we  break file into chunks
        byte[] buffer = new byte[4 * 1024];
        while ((bytes = fileInputStream.read(buffer))
               != -1) {
          // Send the file to Server Socket
          dataOutputStream.write(buffer, 0, bytes);
            dataOutputStream.flush();
        }
        // close the file here
        fileInputStream.close();
    }
}

Server

Here,  we define the ServerSocket object using the ServerSocket class.
Example:

ServerSocket server  = new ServerSocket(port_number)

• when the client sent the request to the server socket. we will call the “receiveFile” method
• We receive the file from the client socket and read the file using the data input stream class
• In this method, we will change the file name and the location of the file. write the file using FileOutputStream Class.

Java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {

    private static DataOutputStream dataOutputStream = null;
    private static DataInputStream dataInputStream = null;

    public static void main(String[] args)
    {
        // Here we define Server Socket running on port 900
        try (ServerSocket serverSocket
             = new ServerSocket(900)) {
            System.out.println(
                "Server is Starting in Port 900");
            // Accept the Client request using accept method
            Socket clientSocket = serverSocket.accept();
            System.out.println("Connected");
            dataInputStream = new DataInputStream(
                clientSocket.getInputStream());
            dataOutputStream = new DataOutputStream(
                clientSocket.getOutputStream());
            // Here we call receiveFile define new for that
            // file
            receiveFile("NewFile1.pdf");

            dataInputStream.close();
            dataOutputStream.close();
            clientSocket.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }

    // receive file function is start here

    private static void receiveFile(String fileName)
        throws Exception
    {
        int bytes = 0;
        FileOutputStream fileOutputStream
            = new FileOutputStream(fileName);

        long size
            = dataInputStream.readLong(); // read file size
        byte[] buffer = new byte[4 * 1024];
        while (size > 0
               && (bytes = dataInputStream.read(
                       buffer, 0,
                       (int)Math.min(buffer.length, size)))
                      != -1) {
            // Here we write the file using write method
            fileOutputStream.write(buffer, 0, bytes);
            size -= bytes; // read upto file size
        }
        // Here we received file
        System.out.println("File is Received");
        fileOutputStream.close();
    }
}

Output: