I am creating a simple Knock Knock application (socket programming) where there is a localhost server and there is a client.the program is simple, the server will tell the knock knock jokes, this is how it's supposed to go,
Server: Knock Knock
Client: Who's there?
Server: Turnip.
Client: Turnip Who?
Server: Turnip the heat.
So that's how the program supposed to go. but the thing is my GUI doesn't show any messages. on my Text area. Here are my codes.
The Server:
import java.net.*;
import java.io.*;
public class KnockKnockServer {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException e) {
System.err.println("Could not listen on port: 4444.");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(
clientSocket.getInputStream()));
String inputLine, outputLine;
KnockKnockProtocol kkp = new KnockKnockProtocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye."))
break;
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
}
The KnockKnockProtocol
import java.net.*;
import java.io.*;
public class KnockKnockProtocol {
private static final int WAITING = 0;
private static final int SENTKNOCKKNOCK = 1;
private static final int SENTCLUE = 2;
private static final int ANOTHER = 3;
private static final int NUMJOKES = 5;
private int state = WAITING;
private int currentJoke = 0;
private String[] clues = { "Turnip", "Little Old Lady", "Atch", "Who", "Who" };
private String[] answers = { "Turnip the heat, it's cold in here!",
"I didn't know you could yodel!",
"Bless you!",
"Is there an owl in here?",
"Is there an echo in here?" };
public String processInput(String theInput) {
String theOutput = null;
if (state == WAITING) {
theOutput = "Knock! Knock!";
state = SENTKNOCKKNOCK;
} else if (state == SENTKNOCKKNOCK) {
if (theInput.equalsIgnoreCase("Who's there?")) {
theOutput = clues[currentJoke];
state = SENTCLUE;
} else {
theOutput = "You're supposed to say \"Who's there?\"! " +
"Try again. Knock! Knock!";
}
} else if (state == SENTCLUE) {
if (theInput.equalsIgnoreCase(clues[currentJoke] + " who?")) {
theOutput = answers[currentJoke] + " Want another? (y/n)";
state = ANOTHER;
} else {
theOutput = "You're supposed to say \"" +
clues[currentJoke] +
" who?\"" +
"! Try again. Knock! Knock!";
state = SENTKNOCKKNOCK;
}
} else if (state == ANOTHER) {
if (theInput.equalsIgnoreCase("y")) {
theOutput = "Knock! Knock!";
if (currentJoke == (NUMJOKES - 1))
currentJoke = 0;
else
currentJoke++;
state = SENTKNOCKKNOCK;
} else {
theOutput = "Bye.";
state = WAITING;
}
}
return theOutput;
}
}
The Client.
import java.io.*;
import java.net.*;
public class KnockKnockClient {
public String fromServer;
public String fromUser;
public void Client() throws IOException {
Socket kkSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
kkSocket = new Socket("127.0.0.1", 4444);
out = new PrintWriter(kkSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: 127.0.0.1");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: 127.0.0.1");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equals("Bye."))
break;
fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
out.close();
in.close();
stdIn.close();
kkSocket.close();
}
}
And The UI
import java.awt.event.ActionListener;
public class KnockKnockWindow extends JFrame {
JTextArea clientTextArea;
JTextArea serverTextArea;
JButton submitButton;
public KnockKnockWindow() {
super("Chat Window");
setVisible(true);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setSize(420,228);
getContentPane().setLayout(null);
clientTextArea = new JTextArea();
clientTextArea.setBounds(10, 118, 278, 51);
getContentPane().add(clientTextArea);
serverTextArea = new JTextArea();
serverTextArea.setBounds(10, 11, 278, 96);
getContentPane().add(serverTextArea);
submitButton = new JButton("Submit");
submitButton.setBounds(298, 118, 89, 51);
getContentPane().add(submitButton);
}
public void setServerText(String fromServer){
serverTextArea.setText(fromServer);
}
public void setClientText(String fromClient){
clientTextArea.setText(fromClient);
}
public String returnClientText(){
return clientTextArea.getText();
}
public void addSubmitListener(ActionListener sub){
submitButton.addActionListener(sub);
}
}
The Controller
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class KnockKnockController {
private KnockKnockClient client;
private KnockKnockWindow window;
public KnockKnockController(KnockKnockClient client, KnockKnockWindow window){
this.client = client;
this.window = window;
window.addSubmitListener(new SubmitListener());
window.setServerText(client.fromServer);
}
public class SubmitListener implements ActionListener{
public void actionPerformed(ActionEvent arg0) {
client.fromUser = window.returnClientText();
}
}
}
And the Main Application
import javax.swing.JFrame;
public class KnockTest extends JFrame{
public static void main (String[] args){
KnockKnockClient kkcl = new KnockKnockClient();
KnockKnockWindow kkw = new KnockKnockWindow();
KnockKnockController kkc = new KnockKnockController(kkcl,kkw);
}
}
We will run the server first, then the main.
But why is it that I am not receiving any messages from the server? when I click start. The text area of the Server should say KnockKnock. but it appears it is not showing, any idea? sorry for the long code post, but I do not know to shorten them here. since I know most of them are important
Where exactly are you printing to the textarea as you are saying the while loop simply gets the text and prints it to the console.
// Put this code somewhere in the Client class so that when it receives something,
// it can be added to the `JTextArea`
while ((fromServer = in.readLine()) != null)
{
// You seems like missed the part that sends it to the textArea
System.out.println("Server: " + fromServer);
// Here send the received thing to your textarea, which goes something like this
String str = "Server : " + fromServer + "\n";
tarea.append(str);
if (fromServer.equals("Bye."))
break;
// You can remove this part and put it inside the textField's actionPerformed method.
fromUser = stdIn.readLine();
if (fromUser != null)
{
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
BRAND NEW EDIT :
Just start your KnockKnockServer from the command prompt, not from your class that extends JFrame. Just simply write java KnockKnockServer, to run your server on the command prompt, now on the new command prompt compile this class i am giving you and run it too like java KnockKnockClient, you will get an idea it's not working fully though.
import java.awt.BorderLayout;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.swing.*;
public class KnockKnockClient extends JFrame
{
public String fromServer;
public String fromUser;
// Added by me.--------------------
private JTextArea tarea;
private JTextField tfield;
private JScrollPane spane;
private PrintWriter out = null;
/*------------------------------------*/
public void Client() throws IOException
{
Socket kkSocket = null;
//PrintWriter out = null; Shifted this to the instance variable
BufferedReader in = null;
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
try {
kkSocket = new Socket("127.0.0.1", 4444);
out = new PrintWriter(kkSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: 127.0.0.1");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: 127.0.0.1");
System.exit(1);
}
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
JPanel contentPane = new JPanel();
tarea = new JTextArea(10, 10);
spane = new JScrollPane(tarea);
tarea.setLineWrap(true);
tfield = new JTextField(10);
tfield.requestFocusInWindow();
contentPane.setLayout(new BorderLayout());
contentPane.add(spane, BorderLayout.CENTER);
contentPane.add(tfield, BorderLayout.PAGE_END);
setContentPane(contentPane);
pack();
setVisible(true);
Thread receiveMessage = new Thread(new ReceiveChat(in, stdIn, out));
receiveMessage.start();
tfield.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
// Here you will send it to the server side too, put that code here
fromUser = tfield.getText() + "\n";
if (fromUser != null)
{
System.out.println("Client: " + fromUser);
tarea.append(fromUser);
out.println(fromUser);
tfield.setText("");
}
}
});
//out.close();
//in.close();
//stdIn.close();
//kkSocket.close();
}
private class ReceiveChat implements Runnable
{
private BufferedReader in;
private BufferedReader stdIn;
private PrintWriter out;
public ReceiveChat(BufferedReader in, BufferedReader stdIn, PrintWriter out)
{
this.in = in;
this.stdIn = stdIn;
this.out = out;
}
public void run()
{
try
{
while ((fromServer = in.readLine()) != null) {
//System.out.println("Server: " + fromServer);
String str = "Server : " + fromServer + "\n";
tarea.append(str);
tarea.setCaretPosition(tarea.getDocument().getLength());
if (fromServer.equals("Bye."))
break;
/*Commented out by me.*/
/*fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
} */
}
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
KnockKnockClient client = new KnockKnockClient();
try
{
client.Client();
}
catch(Exception e)
{
e.printStackTrace();
}
}
});
}
}
Just let the while loop of your KnockKnockServer class look like this :
while ((inputLine = in.readLine()) != null)
{
if (inputLine.length() > 0)
{
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye."))
break;
}
}
This will make it work as expected.
来源：https://stackoverflow.com/questions/9240308/knock-knock-application-with-server-and-ui