Socket Programming over the Internet

[Jude Hapuarachchi]

I wrote a simple chat program which perfectly runs on the local host. But, when the client tries to connect to the server via the Internet using the public IP and the port-9999, it does not work as it did on LAN.

As many people have suggested, I did Port-Forwarding as shown in the following figure.


After configuring Port-Forwarding this website indicates that port-9999 remains open for the specific public IP (I run the server on 192.168.1.100 on private network). Although the port remains open, the client cannot connect to the server. Then I disabled the Windows firewall and tried the same process. But the problem still persists.

Please can someone tell me how can I solve this problem..?

Thanks in advance
Sorry for my bad English

Here is the code of the Chat application..

Server:

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

class Server{
	
	ServerSocket ss;
	Socket s;
	ArrayList al=new ArrayList();
	
	Server(){
		listen(9999);
	}
	
	public static void main(String[] args){
		new Server();
	}
	
	public void listen(int port){
		try{
			ss=new ServerSocket(port);
			
			while(true){
				s=ss.accept();
				
				PrintWriter pw=new PrintWriter(s.getOutputStream(),true);
				al.add(pw);
				new ServerThread(this,s);
			}
			
		}catch(Exception e){System.out.println(e);}
	}
	
	public void sendToAll(String msg){
		try{
			synchronized(al){
				for(int i=0;i<al.size();i++){
					PrintWriter pw=(PrintWriter)al.get(i);
					pw.println(msg);
					pw.flush();
				}
			}
		}catch(Exception e){System.out.println(e);}
	}
	
}

class ServerThread extends Thread{
	
	Server server;
	Socket soc;
	
	ServerThread(Server server, Socket soc){
		this.server=server;
		this.soc=soc;
		start();
	}
	
	public void run(){
		try{
			BufferedReader br=new BufferedReader(new InputStreamReader(soc.getInputStream()));
			
			while(true){
				String msg=br.readLine();
				server.sendToAll(msg);
			}
			
		}catch(Exception e){System.out.println(e);}
	}
}

Client:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.net.*;
import java.io.*;

class Client extends JFrame implements Runnable{
	
	JPanel p1=new JPanel(new BorderLayout());
	JTextField tf=new JTextField();
	JTextArea ta=new JTextArea();
	JLabel lbl1=new JLabel("Message");
	JButton b1=new JButton("Send");
	
	PrintWriter pw;
	BufferedReader br;
	Socket s;
	
	Client(){
		p1.add("West",lbl1);p1.add("Center",tf);p1.add("East",b1);
		
		setLayout(new BorderLayout());
		add("Center",ta);add("South",p1);
		
		try{
			s=new Socket("112.134.190.41",9999);
			pw=new PrintWriter(s.getOutputStream(),true);
			br=new BufferedReader(new InputStreamReader(s.getInputStream()));
		}catch(Exception e){System.out.println(e);}
		
		b1.addActionListener(new ActionListener(){public void actionPerformed(ActionEvent e){send(tf.getText());}});
		
		new Thread(this,s.toString()).start();
		
		setSize(300,400);
		setVisible(true);
	}
	
	public void send(String msg){
		try{
			pw.println(msg);
			pw.flush();
			
		}catch(Exception e){System.out.println(e);}
	}
	
	public static void main(String args[]){
		new Client();
	}
	
	public void run(){
		try{
			while(true){
				ta.append(Thread.currentThread().toString()+br.readLine()+"\n");
			}
		}catch(Exception e){System.out.println(e);}
	}
}