Socket Programming over the Internet

[djmaxtor]

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;
	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){
				Socket 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);}
	}
}

[djmaxtor]

I wrote a simple chat program which perfectly runs on the local host.

What did you mean my friend..?

[javapenguin]

Never mind. That was a spammer. Using AI stuff to copy posts, and it copied your first line, and post semi-relevant stuff, along with possibly links or stuff. That user has been banned.

Anyway, I wasn't aware that ports could be negative.

It looked like you said port -9999.

Perhaps the app isn't granted admin permission on that network.

Your server is the one online, right? Perhaps a possibility is that it's looking for port -9999 or 9999 on its own network, not yours.

[djmaxtor]

Never mind. That was a spammer. Using AI stuff to copy posts, and it copied your first line, and post semi-relevant stuff, along with possibly links or stuff. That user has been banned.

Anyway, I wasn't aware that ports could be negative.

It looked like you said port -9999.

Perhaps the app isn't granted admin permission on that network.

Your server is the one online, right? Perhaps a possibility is that it's looking for port -9999 or 9999 on its own network, not yours.

I think you have misunderstood that I had used -9999 (a negative port). As you said I too wasn't aware that a port could be negative.
As shown in the source code I have used port 9999 for my chat application.

According to my app, the server is the one who remains online and listening to the port 9999. When a client tries to connect to the specific public IP of the server through port 9999, the server accepts the connection and grants the particular service to the client.

After configuring Port-Forwarding this website indicates that port 9999 remains open for the specific public IP where the server listens to the specific port. Although the port remains open, the client cannot connect to the server.

In such a situation how can I create a connections among clients and the server..?

[Voodoo]

djmaxtor
I suppose this IP "112.134.190.41" is the given IP of your provider. What I see in your client program is a "hardwired" code s=new Socket("112.134.190.41",9999);. 2 Questions:
Is this IP static or dynamic?
How you configure your router (i.e. gateway to the web) and your local computer?

By the way, it's better to code Socket s=ss.accept(); than Socket s; ....s=ss.accept(); Reason is that your server can accept MORE incoming requests and only 1 is available and is probably still occupied...

[djmaxtor]

djmaxtor
I suppose this IP "112.134.190.41" is the given IP of your provider. What I see in your client program is a "hardwired" code s=new Socket("112.134.190.41",9999);. 2 Questions:
Is this IP static or dynamic?
How you configure your router (i.e. gateway to the web) and your local computer?

By the way, it's better to code Socket s=ss.accept(); than Socket s; ....s=ss.accept(); Reason is that your server can accept MORE incoming requests and only 1 is available and is probably still occupied...

Thank you so much for your reply my friend,
The given IP is an Dynamic IP. Since I'm not good in Networking, as I know the assigned IP address remain unchanged until I restart my router. So I just need to check whether I can connect two or more socket applications over the internet.

When configuring my router I followed the following procedure
Login to my router configuration page--> Advanced Setup-->NAT-->Virtual Server Setup--> Then entered the information as follows

Then I added an inbound and outbound rule for port 9999 in windows firewall.

Can you please help me to sort out this problem? So that I can continue my project work without any doubts.
Thanks in advance

[Voodoo]

djmaxtor,
it's a very complicated matter. It depends fully on your Router. Because I don't know your Router so recommend you to look at the manuals or ask its tech.support. Normally you have to forward the port and it depends on the feature of your router. Here is the Port Forwarding Guides Listed by Manufacturer and Model - PortForward.com
Your codes are fine. Now it depends only on the Port-Forwarding. Good luck!