socket server

From:
 korcs <konrad.lindner@gmx.net>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 17 Sep 2007 04:31:13 -0700
Message-ID:
<1190028673.372758.84160@57g2000hsv.googlegroups.com>
Hi,

I am quite a newby with socket programing and encountered a problem:

I have a small socket server application, thet echoes the received
strings back to the client.

It works fine, but when the client stops running, the server stops
running as well ("Read Failed").

How should I change the code, that I can handle several client
connections, one-after-another.
(I suppose one should reset the server somehow...)

Is it possible, that I can handle several clients on the same port (I
suppose one should listen on one socket for clients and redirect them
to different server objects listening on different ports...am I
right?)

The code of the Server is the following:

import java.awt.Color;
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;

import java.io.*;
import java.net.*;
import java.util.Vector;

class SocketServer extends JFrame
        implements ActionListener {

   /**
     *
     */
    private static final long serialVersionUID = 1L;

   JButton button;
   JLabel label = new JLabel("Zuletzt empfangene Daten:");
   JPanel panel;
   JTextArea textArea = new JTextArea();
   ServerSocket server = null;
   Socket client = null;
   BufferedReader in = null;
   PrintWriter out = null;
   String line;

   SocketServer(){ //Begin Constructor
     button = new JButton("Zuletzt empfangene Daten ausgeben");
     button.addActionListener(this);

     panel = new JPanel();
     panel.setLayout(new BorderLayout());
     panel.setBackground(Color.white);
     getContentPane().add(panel);
     panel.add("North", label);
     panel.add("Center", textArea);
     panel.add("South", button);

   } //End Constructor

  public void actionPerformed(ActionEvent event) {
     Object source = event.getSource();

     if(source == button){
         textArea.setText(line);
     }
  }

  public void listenSocket(){

    try{
      server = new ServerSocket(4444);
    } catch (IOException e) {
      System.out.println("Could not listen on port 4444");
      System.exit(-1);
    }

    try{
      client = server.accept();
    } catch (IOException e) {
      System.out.println("Accept failed: 4444");
      System.exit(-1);
    }

    try{
      in = new BufferedReader(new
InputStreamReader(client.getInputStream()));
      out = new PrintWriter(client.getOutputStream(), true);
    } catch (IOException e) {
      System.out.println("Accept failed: 4444");
      System.exit(-1);
    }

    while(true){
      try{
        line = in.readLine();
//Send data back to client
        out.println(line);

// Write data into the database

      } catch (IOException e) {
        System.out.println("Read failed");
        System.exit(-1);
      }
    }
  }

  protected void finalize(){
//Clean up
     try{
        in.close();
        out.close();
        server.close();
    } catch (IOException e) {
        System.out.println("Could not close.");
        System.exit(-1);
    }
  }

  public static void main(String[] args){
        SocketServer frame = new SocketServer();
    frame.setTitle("Server Programm");
        WindowListener l = new WindowAdapter() {
                public void windowClosing(WindowEvent e) {
                        System.exit(0);
                }
        };
        frame.addWindowListener(l);
        frame.pack();
        frame.setVisible(true);
    frame.listenSocket();
  }
}

Thanks for your help!

Best,

korcs

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