Java - File Transfer Example Using Socket

This code snippet demonstrates a very simple file transfer program. In this example the client program sends a file to the server. The client program is a GUI and allows a user to browse for a file to send to the server.
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  1. // Client.java
  2.  
  3. /*
  4.  * In this client/server example, the client sends a file to the server.
  5.  *
  6.  */
  7.  
  8. import javax.swing.*;
  9. import java.awt.*;
  10. import java.awt.event.*;
  11. import java.net.*;
  12. import java.io.*;
  13.  
  14. public class Client extends JFrame implements ActionListener {
  15.  
  16.     private JTextField txtFile;
  17.    
  18.     public static void main(String args[]){
  19.  
  20.         /* Create and display the client form */
  21.  
  22.         Client clientForm = new Client();
  23.         clientForm.Display();
  24.     }
  25.  
  26.     public void Display(){
  27.  
  28.         JFrame frame = new JFrame();
  29.         frame.setTitle("Client");
  30.  
  31.         FlowLayout layout = new FlowLayout();
  32.         layout.setAlignment(FlowLayout.LEFT);
  33.  
  34.         JLabel lblFile = new JLabel("Filename:");
  35.        
  36.         txtFile = new JTextField();
  37.         txtFile.setPreferredSize(new Dimension(150,30));
  38.  
  39.         JButton btnTransfer = new JButton("Transfer");
  40.         btnTransfer.addActionListener(this);
  41.  
  42.         JPanel mainPanel = new JPanel();
  43.         mainPanel.setLayout(layout);
  44.         mainPanel.add(lblFile);
  45.         mainPanel.add(txtFile);
  46.         mainPanel.add(btnTransfer);
  47.  
  48.         frame.getContentPane().add(mainPanel);
  49.         frame.pack();
  50.         frame.setVisible(true);
  51.     }
  52.  
  53.     public void actionPerformed(ActionEvent e) {
  54.  
  55.         /* File Open Dialog box allows the user to select a file */
  56.  
  57.         JFileChooser fileDlg = new JFileChooser();
  58.         fileDlg.showOpenDialog(this);
  59.         String filename = fileDlg.getSelectedFile().getAbsolutePath();
  60.         txtFile.setText(filename);
  61.  
  62.         try{
  63.  
  64.             /* Try to connect to the server on localhost, port 5555 */
  65.  
  66.             Socket sk = new Socket("localhost", 5555);
  67.             OutputStream output = sk.getOutputStream();
  68.  
  69.             /* Send filename to server */
  70.  
  71.             OutputStreamWriter outputStream = new OutputStreamWriter(sk.getOutputStream());
  72.             outputStream.write(fileDlg.getSelectedFile().getName() + "\n");
  73.             outputStream.flush();
  74.  
  75.             /* Get reponse from server */
  76.  
  77.             BufferedReader inReader = new BufferedReader(new InputStreamReader(sk.getInputStream()));
  78.  
  79.             String serverStatus = inReader.readLine(); // Read the first line
  80.  
  81.             /* If server is ready, send the file */
  82.  
  83.             if ( serverStatus.equals("READY") ){
  84.  
  85.                 FileInputStream file = new FileInputStream(filename);
  86.  
  87.                 byte[] buffer = new byte[sk.getSendBufferSize()];
  88.  
  89.                 int bytesRead = 0;
  90.  
  91.                 while((bytesRead = file.read(buffer))>0)
  92.                 {
  93.                     output.write(buffer,0,bytesRead);
  94.                 }
  95.  
  96.                 output.close();
  97.                 file.close();
  98.                 sk.close();
  99.  
  100.                 JOptionPane.showMessageDialog(this, "Transfer complete");
  101.             }
  102.         }
  103.         catch (Exception ex){
  104.             /* Catch any errors */
  105.             JOptionPane.showMessageDialog(this, ex.getMessage());
  106.         }
  107.     }
  108. }
  109.  
  110.  
  111. // Server.java
  112.  
  113. /*
  114.  * Server waits for a connection to be established by client
  115.  *
  116.  */
  117.  
  118. import java.io.*;
  119. import java.net.*;
  120.  
  121. class Server
  122. {
  123.     public static void main(String args[])throws Exception
  124.     {
  125.         System.out.println("Server running...");
  126.  
  127.         /* Listen on port 5555 */
  128.  
  129.         ServerSocket server = new ServerSocket(5555);
  130.  
  131.         /* Accept the sk */
  132.  
  133.         Socket sk = server.accept();
  134.        
  135.         System.out.println("Server accepted client");
  136.         InputStream input = sk.getInputStream();
  137.         BufferedReader inReader = new BufferedReader(new InputStreamReader(sk.getInputStream()));
  138.         BufferedWriter outReader = new BufferedWriter(new OutputStreamWriter(sk.getOutputStream()));
  139.  
  140.         /* Read the filename */
  141.         String filename = inReader.readLine();
  142.  
  143.         if ( !filename.equals("") ){
  144.  
  145.             /* Reply back to client with READY status */
  146.  
  147.             outReader.write("READY\n");
  148.             outReader.flush();
  149.         }
  150.  
  151.         /* Create a new file in the tmp directory using the filename */
  152.         FileOutputStream wr = new FileOutputStream(new File("C://tmp/" + filename));
  153.  
  154.         byte[] buffer = new byte[sk.getReceiveBufferSize()];
  155.  
  156.         int bytesReceived = 0;
  157.  
  158.         while((bytesReceived = input.read(buffer))>0)
  159.         {
  160.             /* Write to the file */
  161.            wr.write(buffer,0,bytesReceived);
  162.         }
  163.     }
  164. }

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4 comments:

Vams said...

got error file cannot find

Syed Hussain said...

Hi Vams, sorry for the late reply, can you provide more details, is the file not found on the client or on the server?

Anonymous said...

Arjun Goswami: Create a file in c drive with tmp as name

Dave Batista said...

thank u man

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