Chat for more than 1 users - networking

Question

This is the code for a simple chat that allows 1 user to connect with the server. The other users have to wait in a queue to connect the server, and they are allowed to connect after the user using it determinate the connection. Anyone know how I can make it work, so that more users can chat at the same time together? Here is the Server code:
// Server.java
// Server portion of a client/server stream-socket connection.
import java.io.EOFException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class Server extends JFrame
{
private JTextField enterField; // inputs message from user
private JTextArea displayArea; // display information to user
private ObjectOutputStream output; // output stream to client
private ObjectInputStream input; // input stream from client
private ServerSocket server; // server socket
private Socket connection; // connection to client
private int counter = 1; // counter of number of connections
// set up GUI
public Server()
{
super( "Server" );
enterField = new JTextField(); // create enterField
enterField.setEditable( false );
enterField.addActionListener(
new ActionListener()
{
// send message to client
public void actionPerformed( ActionEvent event )
{
sendData( event.getActionCommand() );
enterField.setText( "" );
} // end method actionPerformed
} // end anonymous inner class
); // end call to addActionListener
add( enterField, BorderLayout.NORTH );
displayArea = new JTextArea(); // create displayArea
add( new JScrollPane( displayArea ), BorderLayout.CENTER );
setSize( 300, 150 ); // set size of window
setVisible( true ); // show window
} // end Server constructor
// set up and run server
public void runServer()
{
try // set up server to receive connections; process connections
{
server = new ServerSocket( 12345, 100 ); // create ServerSocket
while ( true )
{
try
{
waitForConnection(); // wait for a connection
getStreams(); // get input & output streams
processConnection(); // process connection
} // end try
catch ( EOFException eofException )
{
displayMessage( "\nServer terminated connection" );
} // end catch
finally
{
closeConnection(); // close connection
++counter;
} // end finally
} // end while
} // end try
catch ( IOException ioException )
{
ioException.printStackTrace();
} // end catch
} // end method runServer
// wait for connection to arrive, then display connection info
private void waitForConnection() throws IOException
{
displayMessage( "Waiting for connection\n" );
connection = server.accept(); // allow server to accept connection
displayMessage( "Connection " + counter + " received from: " +
connection.getInetAddress().getHostName() );
} // end method waitForConnection
// get streams to send and receive data
private void getStreams() throws IOException
{
// set up output stream for objects
output = new ObjectOutputStream( connection.getOutputStream() );
output.flush(); // flush output buffer to send header information
// set up input stream for objects
input = new ObjectInputStream( connection.getInputStream() );
displayMessage( "\nGot I/O streams\n" );
} // end method getStreams
// process connection with client
private void processConnection() throws IOException
{
String message = "Connection successful";
sendData( message ); // send connection successful message
// enable enterField so server user can send messages
setTextFieldEditable( true );
do // process messages sent from client
{
try // read message and display it
{
message = ( String ) input.readObject(); // read new message
displayMessage( "\n" + message ); // display message
} // end try
catch ( ClassNotFoundException classNotFoundException )
{
displayMessage( "\nUnknown object type received" );
} // end catch
} while ( !message.equals( "CLIENT>>> TERMINATE" ) );
} // end method processConnection
// close streams and socket
private void closeConnection()
{
displayMessage( "\nTerminating connection\n" );
setTextFieldEditable( false ); // disable enterField
try
{
output.close(); // close output stream
input.close(); // close input stream
connection.close(); // close socket
} // end try
catch ( IOException ioException )
{
ioException.printStackTrace();
} // end catch
} // end method closeConnection
// send message to client
private void sendData( String message )
{
try // send object to client
{
output.writeObject( "SERVER>>> " + message );
output.flush(); // flush output to client
displayMessage( "\nSERVER>>> " + message );
} // end try
catch ( IOException ioException )
{
displayArea.append( "\nError writing object" );
} // end catch
} // end method sendData
// manipulates displayArea in the event-dispatch thread
private void displayMessage( final String messageToDisplay )
{
SwingUtilities.invokeLater(
new Runnable()
{
public void run() // updates displayArea
{
displayArea.append( messageToDisplay ); // append message
} // end method run
} // end anonymous inner class
); // end call to SwingUtilities.invokeLater
} // end method displayMessage
// manipulates enterField in the event-dispatch thread
private void setTextFieldEditable( final boolean editable )
{
SwingUtilities.invokeLater(
new Runnable()
{
public void run() // sets enterField's editability
{
enterField.setEditable( editable );
} // end method run
} // end inner class
); // end call to SwingUtilities.invokeLater
} // end method setTextFieldEditable
} // end class Server
+
// Test the Server application.
import javax.swing.JFrame;
public class ServerTest
{
public static void main( String[] args )
{
Server application = new Server(); // create server
application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
application.runServer(); // run server application
} // end main
}
And the Client code:
Client.java
// Client portion of a stream-socket connection between client and server.
import java.io.EOFException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class Client extends JFrame
{
private JTextField enterField; // enters information from user
private JTextArea displayArea; // display information to user
private ObjectOutputStream output; // output stream to server
private ObjectInputStream input; // input stream from server
private String message = ""; // message from server
private String chatServer; // host server for this application
private Socket client; // socket to communicate with server
// initialize chatServer and set up GUI
public Client( String host )
{
super( "Client" );
chatServer = host; // set server to which this client connects
enterField = new JTextField(); // create enterField
enterField.setEditable( false );
enterField.addActionListener(
new ActionListener()
{
// send message to server
public void actionPerformed( ActionEvent event )
{
sendData( event.getActionCommand() );
enterField.setText( "" );
} // end method actionPerformed
} // end anonymous inner class
); // end call to addActionListener
add( enterField, BorderLayout.NORTH );
displayArea = new JTextArea(); // create displayArea
add( new JScrollPane( displayArea ), BorderLayout.CENTER );
setSize( 300, 150 ); // set size of window
setVisible( true ); // show window
} // end Client constructor
// connect to server and process messages from server
public void runClient()
{
try // connect to server, get streams, process connection
{
connectToServer(); // create a Socket to make connection
getStreams(); // get the input and output streams
processConnection(); // process connection
} // end try
catch ( EOFException eofException )
{
displayMessage( "\nClient terminated connection" );
} // end catch
catch ( IOException ioException )
{
ioException.printStackTrace();
} // end catch
finally
{
closeConnection(); // close connection
} // end finally
} // end method runClient
// connect to server
private void connectToServer() throws IOException
{
displayMessage( "Attempting connection\n" );
// create Socket to make connection to server
client = new Socket( InetAddress.getByName( chatServer ), 12345 );
// display connection information
displayMessage( "Connected to: " +
client.getInetAddress().getHostName() );
} // end method connectToServer
// get streams to send and receive data
private void getStreams() throws IOException
{
// set up output stream for objects
output = new ObjectOutputStream( client.getOutputStream() );
output.flush(); // flush output buffer to send header information
// set up input stream for objects
input = new ObjectInputStream( client.getInputStream() );
displayMessage( "\nGot I/O streams\n" );
} // end method getStreams
// process connection with server
private void processConnection() throws IOException
{
// enable enterField so client user can send messages
setTextFieldEditable( true );
do // process messages sent from server
{
try // read message and display it
{
message = ( String ) input.readObject(); // read new message
displayMessage( "\n" + message ); // display message
} // end try
catch ( ClassNotFoundException classNotFoundException )
{
displayMessage( "\nUnknown object type received" );
} // end catch
} while ( !message.equals( "SERVER>>> TERMINATE" ) );
} // end method processConnection
// close streams and socket
private void closeConnection()
{
displayMessage( "\nClosing connection" );
setTextFieldEditable( false ); // disable enterField
try
{
output.close(); // close output stream
input.close(); // close input stream
client.close(); // close socket
} // end try
catch ( IOException ioException )
{
ioException.printStackTrace();
} // end catch
} // end method closeConnection
// send message to server
private void sendData( String message )
{
try // send object to server
{
output.writeObject( "CLIENT>>> " + message );
output.flush(); // flush data to output
displayMessage( "\nCLIENT>>> " + message );
} // end try
catch ( IOException ioException )
{
displayArea.append( "\nError writing object" );
} // end catch
} // end method sendData
// manipulates displayArea in the event-dispatch thread
private void displayMessage( final String messageToDisplay )
{
SwingUtilities.invokeLater(
new Runnable()
{
public void run() // updates displayArea
{
displayArea.append( messageToDisplay );
} // end method run
} // end anonymous inner class
); // end call to SwingUtilities.invokeLater
} // end method displayMessage
// manipulates enterField in the event-dispatch thread
private void setTextFieldEditable( final boolean editable )
{
SwingUtilities.invokeLater(
new Runnable()
{
public void run() // sets enterField's editability
{
enterField.setEditable( editable );
} // end method run
} // end anonymous inner class
); // end call to SwingUtilities.invokeLater
} // end method setTextFieldEditable
} // end class Client
+
// Class that tests the Client.
import javax.swing.JFrame;
public class ClientTest
{
public static void main( String[] args )
{
Client application; // declare client application
// if no command line args
if ( args.length == 0 )
application = new Client( "127.0.0.1" ); // connect to localhost
else
application = new Client( args[ 0 ] ); // use args to connect
application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
application.runClient(); // run client application
} // end main
}

Answer 1

After seeing ur program, this is what is going wrong.You are using exactly ONE thread as the server and u are blocking this thread when you call listener.accept().
To avoid this is what you need to do:
Make another class
Server2 - Similar to what you have now, but instead of doing the actual work of acting as an echo server, it just spawns a new Thread which starts listening on a NEW PORT (which you can select randomly), and sends the client the address for this new port. The client will then get the new port number and would try to connect to the server on the new port. 2: The Echo thread - This starts a new listener on the port passed, and does the job of echoing to whoever is listening.
OR:
You start a UDP server rather than a TCP server, and all this will not matter