AppletTalk.com

[Max010]

Hi there I was wondering if anyone can help me please.

I ve been working on a simple chat server program and it works when the
server handles one client at the time. I ve been trying to make the
server able to answer clients requests at the same time with threads.

I always get the same error message when I run the server:

java.lang.NullPointerException

at chatserverq3.ServerGUI.processClientRequests(ServerGUI.java:113)

at chatserverq3.ServerGUI.run(ServerGUI.java:73)

at java.lang.Thread.run(Thread.java:484)

This is the client code:

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


public class ClientGUI extends JFrame implements ActionListener
{
private JTextField nameField;
private JLabel nameLabel;
private JLabel areaLabel;
private JPanel topPanel, botPanel;
private JButton connectButton;
private JTextArea listArea;

private InputStream is;
private OutputStream os;
private BufferedReader fromServer;
private Socket socket;
private PrintWriter toServer;


static final String SERVER_ADDRESS = "127.0.0.1";
static final int SERVER_PORT_NUMBER = 4000;
static final String CLIENT_LOGGINGOFF = "Exit";

//constructor for the client GUI
public ClientGUI(String title)
{
setSize(400, 400);
setTitle(title);
setLocation(100, 100);
nameLabel = new JLabel("Name");
nameField = new JTextField(10);
areaLabel = new JLabel("Connected Users");
topPanel = new JPanel();
topPanel.setLayout(new BorderLayout());
botPanel = new JPanel();
connectButton = new JButton("Connect");
connectButton.addActionListener(this);
listArea = new JTextArea(10, 30);
JScrollPane scr = new JScrollPane(listArea);

topPanel.add(nameField, "West");
topPanel.add(nameLabel, "Center");
topPanel.add(connectButton, "East");

botPanel.add(areaLabel);
botPanel.add(listArea);

getContentPane().add(topPanel, "North");
getContentPane().add(botPanel, "Center");

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

//attempts to connect the client to the server
private void connectServer()
{
try
{
socket = new Socket(SERVER_ADDRESS, SERVER_PORT_NUMBER);
openStreams();
}
catch(IOException e)
{
System.out.println("Trouble contacting the server " + e);
}
}

private void open()throws IOException
{
final boolean AUTO_FLUSH = true;
is = socket.getInputStream();
fromServer = new BufferedReader(new InputStreamReader(is));
os = socket.getOutputStream();
toServer = new PrintWriter(os, AUTO_FLUSH);
}

//action performed when the client GUI button is pressed
public void actionPerformed(ActionEvent a)
{
String buttonLabel = connectButton.getText();
String userName = nameField.getText();
try
{
if((buttonLabel == "Connect")&&(userName.length()> 0))
{
connectToServer();
sendUserName(userName);
connectButton.setText("Disconnect");
}
else
{
logOff(userName);
connectButton.setText("Connect");
}

}
catch(IOException e)
{
System.out.println("Problem with the server " + e);
}
}

private void close()throws IOException
{
toServer.close();
os.close();
fromServer.close();
is.close();
}

//sends the user name to the server
private void sendUserName(String aName)throws IOException
{
String reply;
String uName = aName;
toServer.println(uName + " logged on");

reply = fromServer.readLine();
listArea.setText(reply);
}

//notifies the server a client has logged off
private void logOff(String aName)throws IOException
{
String uName = aName;
toServer.println(uName + " logged off");
listArea.setText("");
toServer.println(CLIENT_LOGGINGOFF);
closeStreams();
socket.close();
}
}

public class Main {

public static void main(String[] args)
{
ClientGUI cg = new ClientGUI("ChatClient");
cg.setVisible(true);
}

}

The server code is:


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

public class ServerGUI extends JFrame implements Runnable
{
private JTextArea logArea;
private JLabel logLabel;
private JPanel logPanel;

private ServerSocket ss;
private Socket socket;

private InputStream is;
private OutputStream os;

private PrintWriter toClient;
private BufferedReader fromClient;

static final int PORT_NUMBER = 4000;
static final String CLIENT_LOGGINGOFF = "Exit";

//constructor for the Server GUI
public ServerGUI(String title)
{
setSize(400, 400);
setTitle(title);
setLocation(100, 100);
logArea = new JTextArea(15, 30);
JScrollPane scr = new JScrollPane(logArea);
logLabel = new JLabel("Logging history");

logPanel = new JPanel();
logPanel.add(logLabel);
logPanel.add(logArea);

getContentPane().add(logPanel);



setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

//constructor for the server to set the socket to handle a new thread
public ServerGUI(Socket s)
{
socket = s;
}



public void run()
{
try
{
while(true)
{

openStreams();
processClientRequests();
closeStreams();
socket.close();
}
}
catch(IOException e)
{
System.out.println("Trouble with a connection " + e);
}

}

//helper method for the class to set up the streams
private void open() throws IOException
{
final boolean AUTO_FLUSH = true;
is = socket.getInputStream();
fromClient = new BufferedReader(new InputStreamReader(is));
os = socket.getOutputStream();
toClient = new PrintWriter(os, AUTO_FLUSH);
}

//process the string from received from each client
private void processRequests() throws IOException
{
String userName;
String reply;
int numberOfFields = 3;
String [] fieldContents = new String[numberOfFields];
userName = fromClient.readLine();
while(!(userName.equals(CLIENT_LOGGINGOFF)))
{
StringTokenizer tokensIn = new StringTokenizer(userName, " ");
int i = 0;
while(tokensIn.hasMoreTokens())
{
fieldContents[i] = tokensIn.nextToken();
i++;
}

reply = fieldContents[0];
toClient.println(reply);
logArea.append("[ " + reply + " ] "+ fieldContents[1]+"
"+fieldContents[2]+"n");
userName = fromClient.readLine();
}
}

//helper method to close the streams with each client
private void close() throws IOException
{
toClient.close();
os.close();
fromClient.close();
is.close();
}
}

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

public class ChatHandler
{
static final int PORT_NUMBER = 4000;

public ChatHandler()
{
}

public void run()
{
try
{
ServerSocket server = new ServerSocket(PORT_NUMBER);
while(true)
{
Socket client = server.accept ();
System.out.println ("Accepted from " + client.getInetAddress ());
Thread aThread = new Thread(new ServerGUI(client));
aThread.start ();
}
}
catch(IOException e)
{
System.out.println("Trouble with ServerSocket, port
"+PORT_NUMBER +": " + e);
}
}
}


public class Main {

public static void main(String[] args)
{
ServerGUI sg = new ServerGUI("ChatServer");
sg.setVisible(true);
ChatHandler cH = new ChatHandler();
cH.run();
}

}


It is the first time I use threads and maybe there is something I dont
understand. Can anyone point me to the right direction please? I think
the problem may be with the 2 server constructor but I am not sure how
to solve it.

Cheers Pat

[Sean]

On

[Max010]

Hi Sean thanks for replying to my message and dont worry about being
hard on me. I am a bit slow with this topic bare with me. I ve made
some adjustment to my program and now it works but every time I run the
client and click on the connect button a new server GUI is started.
For every client GUI there is one server GUI. I would like to have
only one server GUI that displays all the user name that logged on to
the server how do I achieve that?

thanks Pat



//start of the main class
public class Main {

public static void main(String[] args)
{
HandleAClient hAc = new HandleAClient();
hAc.run();
}

}
//end of main class

//start of ServerGUI class
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.util.*;

public class ServerGUI extends JFrame implements Runnable
{
private JTextArea logArea;
private JLabel logLabel;
private JPanel logPanel;

private ServerSocket ss;
private Socket socket;

private InputStream is;
private OutputStream os;

private PrintWriter toClient;
private BufferedReader fromClient;

static final int PORT_NUMBER = 4000;
static final String CLIENT_LOGGINGOFF = "Exit";

public ServerGUI(String title,Socket s)
{
socket = s;
setSize(400, 400);
setTitle(title);
setLocation(100, 100);
logArea = new JTextArea(15, 30);
JScrollPane scr = new JScrollPane(logArea);
logLabel = new JLabel("Logging history");

logPanel = new JPanel();
logPanel.add(logLabel);
logPanel.add(logArea);

getContentPane().add(logPanel);

setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

public void run()
{
try
{
while(true)
{

openStreams();
processClientRequests();
closeStreams();
socket.close();
}
}
catch(IOException e)
{
System.out.println("Trouble with a connection "+e);
}

}

private void openStreams() throws IOException
{
final boolean AUTO_FLUSH = true;
is = socket.getInputStream();
fromClient=new BufferedReader(new InputStreamReader(is));
os = socket.getOutputStream();
toClient = new PrintWriter(os, AUTO_FLUSH);
}

private void processClientRequests() throws IOException
{
String userName;
String reply;
int numberOfFields = 3;
String [] fieldContents = new String[numberOfFields];
userName = fromClient.readLine();
while(!(userName.equals(CLIENT_LOGGINGOFF)))
{
StringTokenizer tokensIn =new StringTokenizer(userName, "
");
int i = 0;
while(tokensIn.hasMoreTokens())
{
fieldContents[i] = tokensIn.nextToken();
i++;
}

reply = fieldContents[0];
toClient.println(reply);
logArea.append("[ " + reply + " ] "+ fieldContents[1]+"
"+fieldContents[2]+"n");
userName = fromClient.readLine();
}
}

private void closeStreams() throws IOException
{
toClient.close();
os.close();
fromClient.close();
is.close();
}
}
//end of class


//start of handle a client class
import java.io.*;
import java.net.*;

public class HandleAClient
{

static final int PORT_NUMBER = 4000;

public HandleAClient()
{
}

public void run()
{
try
{
ServerSocket ss = new ServerSocket(PORT_NUMBER);
while(true)
{
Socket client = ss.accept();
Thread session = new Thread(new ServerGUI("chatServer4",
client));
session.start();
}
}
catch(IOException e)
{
System.out.println("Trouble with ServerSocket , port
"+PORT_NUMBER +": " + e);
}
}
}
//end of class

[Andrew Thompson]

On 22 Aug 2005 07:12:24 -0700, Max010 wrote:

[Thomas Fritsch]

"Max010" <patacca (AT) hotmail (DOT) co.uk> wrote:

[Max010]

Thanks Thomas but I ve been working on the program and now it works but
every time I launch the client frame a server frame comes up.

What I m trying to achieve is to launch several clients (no problem
with that) and only one server frame that record all the clients that
logged on and off.
Here is the server code:
//start of server class
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.util.*;

public class ServerGUI extends JFrame implements Runnable
{
private JTextArea logArea;
private JLabel logLabel;
private JPanel logPanel;

private ServerSocket ss;
private Socket socket;

private InputStream is;
private OutputStream os;

private PrintWriter toClient;
private BufferedReader fromClient;
private ArrayList historyUser = new ArrayList();
static final int PORT_NUMBER = 4000;
static final String CLIENT_LOGGINGOFF = "Exit";

//I ve created a HandleAClient class that listen for client connections
and every time that one clients request a connection it creates a
thread using the ServerGUI constructor. Line 17 is what does that in
the HandleAClient class see below.

public ServerGUI(String title,Socket s)
{
socket = s;
setSize(400, 400);
setTitle(title);
setLocation(100, 100);
logArea = new JTextArea(15, 30);
JScrollPane scr = new JScrollPane(logArea);
logLabel = new JLabel("Logging history");

logPanel = new JPanel();
logPanel.add(logLabel);
logPanel.add(logArea);

getContentPane().add(logPanel);

setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

public void run()
{
try
{
while(true)
{

openStreams();
processClientRequests();
closeStreams();
socket.close();
}
}
catch(IOException e)
{
System.out.println("Trouble with a connection "+e);
}

}

private void openStreams() throws IOException
{
final boolean AUTO_FLUSH = true;
is = socket.getInputStream();
fromClient=new BufferedReader(new InputStreamReader(is));
os = socket.getOutputStream();
toClient = new PrintWriter(os, AUTO_FLUSH);
}

private synchronized void processClientRequests() throws IOException
{
String userName;
String reply;
int numberOfFields = 3;
String [] fieldContents = new String[numberOfFields];

userName = fromClient.readLine();
while(!(userName.equals(CLIENT_LOGGINGOFF)))
{
StringTokenizer tokensIn =new StringTokenizer(userName, "
");
int i = 0;
while(tokensIn.hasMoreTokens())
{
fieldContents[i] = tokensIn.nextToken();
i++;
}

reply = fieldContents[0];
addUserToList(reply);
toClient.println(broadcast().toString());
logArea.append("[ " + reply + " ] "+ fieldContents[1]+"
"+fieldContents[2]+"n");
userName = fromClient.readLine();
}
}

private synchronized void addUserToList(String aUser)
{
while(historyUser.size()>= 0)
{
try
{
wait();
}
catch (InterruptedException e)
{
String errMessage = e.getMessage();
System.out.println("Error "+ errMessage);
}

historyUser.add(aUser);
notifyAll();
System.out.println(aUser);
}
}

private synchronized ArrayList broadcast()
{
ArrayList usersLogged = new ArrayList();
Iterator listIt = historyUser.iterator();
while(listIt.hasNext())
{


usersLogged.add(listIt.next());
}


return usersLogged;
}

private void closeStreams() throws IOException
{
toClient.close();
os.close();
fromClient.close();
is.close();
}
}
//end of server class



//start of HandleAClient class
import java.io.*;
import java.net.*;

public class HandleAClient
{

static final int PORT_NUMBER = 4000;

public HandleAClient()
{
}

public void run()
{
try
{
ServerSocket ss = new ServerSocket(PORT_NUMBER);
while(true)
{
Socket client = ss.accept();
//line 17 Thread session = new Thread(new
ServerGUI("chatServer4", client));
//unfortunately every time the ServerGUI constructor is called a new
frame appears. How can I create a thread to handle a client without
creating a server frame??? Maybe I m doing it all wrong and there s
another strategy I could follow up any suggestion please?
session.start();
}
}
catch(IOException e)
{
System.out.println("Trouble with ServerSocket , port
"+PORT_NUMBER +": " + e);
}
}
}

Regards Pat

[Roedy Green]

On 23 Aug 2005 12:47:18 -0700, "Max010" <patacca (AT) hotmail (DOT) co.uk> wrote
or quoted :