Applet + Application communication

[john price]

Just got an idea for an Applet to Application program...
Using TCP/IP...
So basically, the client is the Applet. The application is the server (1 application running, any number of Applets running). The Application's IP is dynamic. A different Application connects to the Applet to tell it it's IP address. Then, the stream closes. The Applet then connects to the regular Application. Is this possible? If I do this, can I avoid signing it (I know this is an applet question, but I feel it is okay because it deals with sockets and IP)?

Thanks,
cc11rocks

EDIT (Clarification) : There will be two applications running...One is for telling the Applet it's IP address (That is the "different Application" part). The other is the main server.

[Rob Spoor]

An applet can only connect to the very same server it's downloaded from, and you can use getCodeBase() or getDocumentBase() to get a URL from which you can receive the server. If you want to connect to anything else you will have to sign the applet.

I'll still move this thread to our Applets forum since it's an applet specific problem.

[john price]

So I made the Client (Applet, just a simple test) :

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

public class AppletClient extends JApplet {
Socket sock;
BufferedReader reader;
PrintWriter writer;
JTextField no = new JTextField("HI");

@SuppressWarnings("unchecked") 
public static void main (String[] args) {
new AppletClient();
}
public void init() {
JButton go = new JButton("GO");
go.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent afc) {
try {
writer.println("Hello world");
writer.flush();
System.out.println("complete");
}
catch (Exception exa) {
exa.printStackTrace();
}
}
});
add(no, BorderLayout.NORTH);
add(go, BorderLayout.SOUTH);
try {
 sock = new Socket("70.162.171.240", 5000); //My IP
InputStreamReader streamReader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(streamReader);
writer = new PrintWriter(sock.getOutputStream());
writer.println("Random String");
 writer.flush();
}
catch (Exception ex) {
ex.printStackTrace();
}

}
}

Then, I made the Server (Application) :

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

public class AppletServer {
ArrayList clientOutputStreams;
	public class ClientHandler implements Runnable {
		BufferedReader reader;
		Socket sock;
		public ClientHandler(Socket clientSocket) {
			try {
				sock = clientSocket;
				InputStreamReader isReader = new InputStreamReader(sock.getInputStream());
				reader = new BufferedReader(isReader);
				}
			catch(Exception ex) {
				//System.out.println("from server");
				//System.out.println("INSIDE ClientHandler");
				ex.printStackTrace();
			}
		}
	public void run() {
	String message;
		try {
			while ((message = reader.readLine()) != null) {
			System.out.println("read " + message);
			tellEveryone(message);
		}	
		}
		catch(Exception ex) {
		ex.printStackTrace();
		}
	}
	}
@SuppressWarnings("unchecked") 
public static void main (String[] args) {
new AppletServer().go();
}
@SuppressWarnings("unchecked") 
public void go() {
clientOutputStreams = new ArrayList();
	try {
	ServerSocket serverSock = new ServerSocket(5000);
		while(true) {
		Socket clientSocket = serverSock.accept();
		PrintWriter writer = new PrintWriter(clientSocket.getOutputStream());
		clientOutputStreams.add(writer);
		Thread t = new Thread(new ClientHandler(clientSocket));
		t.start();
		System.out.println("got a connection");
		}
	}
	catch(Exception ex) {
	//System.out.println("From System");
	ex.printStackTrace();
	}
}
public void tellEveryone(String message) {
Iterator it = clientOutputStreams.iterator();
	while(it.hasNext()) {
		try {
		PrintWriter writer = (PrintWriter) it.next();
		writer.println(message);
		writer.flush();
		}
		catch(Exception ex) {
		//System.out.println("From System");
		ex.printStackTrace();
		}
	}
	}
}

I made the Applet into a signed JAR. I put it unto a test website ( http://appletclient.webs.com ).
NOTE: The Applet is still on the website. My server may not be up if you go to it...

I started my server. I then went to the website. I accepted the certificate. It successfully sent the data expected to my Server. Then, I had a friend try ( on a different computer, different IP address). He accepted the certificate, but nothing happened on the Server part. Why didn't this work? It is signed and certificated (check it out for yourself). It works fine if I got to the link. How can I make this work?

Thanks,
cc11rocks

EDIT: Yes, I do have port forwarding enabled for port 5000. I'm very eager to get this working...

[john price]

Got it working. Had to add one line to main (the very first line) :

public static void main(String[] args) {
System.getSecurityManager().checkPermission(new SocketPermission("xxx.xxx.xxx.xxx", "connect"));
//xxx.xxx.xxx.xxx = Server IP address
new ClassName();
}

Just a thought (Unrelated) : Why are my post now being ignored? It seems the farther I go in the Java community, the less help I get. I mean, I eventually can solve most of my problems, but I need support guys. Well, anyway, thanks for helping. I really have enjoyed my stay here (I'm not leaving right now).

,
cc11rocks