// Fig. 27.5: Server.java
// Server portion of a client/server stream-socket connection

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;
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, 250);              // set size of window
        setLocation(302, 0);            // set location
        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.equalsIgnoreCase("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