Andy Richard

Tony Docherty wrote:The first exception is thrown because the socket was unable to connect to anything. Presumably you don't have anything listening for a connection on port 4000 on the localhost.

What does that means?
How can i make something listen to that port ??

Well guys, i'm totally new to Java..
I made the following stuff.. it runs, but no action is performed when i try to send it.
The cod is,


package javaapplication14; import java.io.*; import java.net.*; import java.util.*; import javax.swing.*; import java.awt.*; import java.awt.event.*; public class JavaApplication14 { JTextArea incoming; JTextField outgoing; BufferedReader reader; PrintWriter writer; Socket sock; public static void main(String[] args) { JavaApplication14 client = new JavaApplication14(); client.go(); } public void go(){ JFrame frame = new JFrame("Simple Chat Server"); JPanel panel = new JPanel(); incoming = new JTextArea(40, 50); JScrollPane scroller = new JScrollPane(incoming); scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS); scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER); outgoing = new JTextField(20); JButton button = new JButton("SEND"); button.addActionListener(new SendButtonListener()); panel.add( scroller); panel.add(outgoing); panel.add(button); setUpNetworking(); Thread thread = new Thread(new IncomingReader()); thread.start(); frame.getContentPane().add(BorderLayout.CENTER , panel); frame.setSize(500, 500); frame.setVisible(true); } private void setUpNetworking(){ try{ sock = new Socket("127.0.0.1" , 4000); InputStreamReader streamReader = new InputStreamReader(sock.getInputStream()); reader = new BufferedReader(streamReader); writer = new PrintWriter(sock.getOutputStream()); System.out.println("Network Established"); }catch(IOException ex){ ex.printStackTrace(); } } public class SendButtonListener implements ActionListener{ public void actionPerformed(ActionEvent ev){ writer.println(outgoing.getText()); writer.flush(); outgoing.setText(""); outgoing.requestFocus(); } } public class IncomingReader implements Runnable{ public void run(){ String message; try{ while((message = reader.readLine())!= null){ System.out.println("Read" + message); incoming.append(message + "\n"); } }catch(IOException ex){ ex.printStackTrace(); } } } }
The errors i got are..
run:
java.net.ConnectException: Connection refused: connect at java.net.DualStackPlainSocketImpl.connect0(Native Method) at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) at java.net.Socket.connect(Socket.java:579) at java.net.Socket.connect(Socket.java:528) at java.net.Socket.<init>(Socket.java:425) at java.net.Socket.<init>(Socket.java:208) at javaapplication14.JavaApplication14.setUpNetworking(JavaApplication14.java:51) at javaapplication14.JavaApplication14.go(JavaApplication14.java:38) at javaapplication14.JavaApplication14.main(JavaApplication14.java:21) Exception in thread "Thread-1" java.lang.NullPointerException at javaapplication14.JavaApplication14$IncomingReader.run(JavaApplication14.java:74) at java.lang.Thread.run(Thread.java:744) Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at javaapplication14.JavaApplication14$SendButtonListener.actionPerformed(JavaApplication14.java:63) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) at java.awt.Component.processMouseEvent(Component.java:6505) at javax.swing.JComponent.processMouseEvent(JComponent.java:3320) at java.awt.Component.processEvent(Component.java:6270) at java.awt.Container.processEvent(Container.java:2229) at java.awt.Component.dispatchEventImpl(Component.java:4861) at java.awt.Container.dispatchEventImpl(Container.java:2287) at java.awt.Component.dispatchEvent(Component.java:4687) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422) at java.awt.Container.dispatchEventImpl(Container.java:2273) at java.awt.Window.dispatchEventImpl(Window.java:2719) at java.awt.Component.dispatchEvent(Component.java:4687) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735) at java.awt.EventQueue.access$200(EventQueue.java:103) at java.awt.EventQueue$3.run(EventQueue.java:694) at java.awt.EventQueue$3.run(EventQueue.java:692) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87) at java.awt.EventQueue$4.run(EventQueue.java:708) at java.awt.EventQueue$4.run(EventQueue.java:706) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) at java.awt.EventQueue.dispatchEvent(EventQueue.java:705) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138) at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
I don't understand any part of error here..What exactly are these errrors, and how to re-solve 'em ??

nvm, m cleared!

after going through a few articles, i understood that the number of sockets a port can have depends on the OS.. but, i still wonder what that number is??
For win , linux ??

well Chan,
i edited to the actual error i got.. i placed tat whole stuff in a 'javaApplication9' package.. and a JavaApplication Class.. so just to make it look good name wise, i made the name as check here.
You are right, its the same error i'm getting you talked about..
But, how should i resolve the compilation error i get??

@Chan
This is the error i got..
Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - unreported exception java.lang.ClassNotFoundException; must be caught or declared to be thrown at check.Check.main(Check.java:33)

I just made my first I/O code stuff..just to implement what i read and understood.
But the following code produces error..

import java.io.*; public class check implements Serializable { //Make two variables and methods to initialise them private int height; private int width; public void setWidth(int w){ width = w; } public void setHeight(int h){ height = h; } public static void main(String[] args) { check obj = new check(); obj.setHeight(20); obj.setWidth(30); try{ FileOutputStream fs = new FileOutputStream("foo.txt"); ObjectOutputStream os = new ObjectOutputStream(fs); os.writeObject(obj); os.close(); } catch(IOException ex){ } //We set them to null so we can't access the objects on heap. obj = null; //Now we read them back from file try{ ObjectInputStream is = new ObjectInputStream(new FileInputStream("foo.txt")); check stored = (check) is.readObject(); //Check to see if it worked. System.out.println("Variable, stored contains.." + stored.getType()); } catch(Exception ex){ ex.printStackTrace(); } }
Can anyone help me with that??

@CampBell yeah, i got cleared to that!!

And i still don't understand why is there a need for it.. ??? :\

It's given on page- 364 !!
The para just above the code.

okay, i got my doubt cleared.
But what's hassling me now is that, why you need to paint the frame (panel) again when focus changes?
there is no such need in case of non-graphics stuffs...like we never make our whole say, a hello world program , to execute again on focus change... so why is there a need in case of GUI-based stuffs ??
btw,
i read it in the book... Head First Java.

Also, what is meant by saying that..
"You can't get the object by itself" ???

I read this in a book..
"
The argument to the method paintComponent( ) (i.e; a Graphics object) is the actual drawing canvas that gets slapped onto the real display. You can't get this by yourself; it must be handled to you by the system. You can ask the sysytem to refresh the display ( repaint() ), which ultimately leads to paintComponent() being called.
"
So, i don't understand why is there a need to call the paintComponent( ) everytime? liike it's called when you minimize/maximize the frame.. etc.
this is not the case with widgets like buttons, checkboxes, textareas... many more.
then why is this the case with paintComponent( ) ??

Tony Docherty wrote:
It can if it is the same package. If you want methods/variables to be accessible to sub classes in external packages then mark them as protected.

you sure ??
:O
then what's the difference in protected specifier ??

Tony Docherty wrote:
Why not try it and see what happens.

it isn't accessible.. ?
:\