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How do I put a Server class on my website so my Client class can communicate with it from different computers?

I have a server client application working just how I want it locally. I need to get the server online so the client program can be used from different computers. Not sure how to do this. I have my own website that I thought I could just put the Server on in the background.
Is this possible or am I just looking at this the wrong way.
Server.java
package core;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Scanner;
public class Server {
public static void main(String[] args) throws IOException {
ArrayList<ClientHandler> clients = new ArrayList<>();
ServerSocket serverSocket = null;
int clientNum = 1; // keeps track of how many clients were created
// 1. CREATE A NEW SERVERSOCKET
try {
serverSocket = new ServerSocket(4444); // provide MYSERVICE at port
// 4444
} catch (IOException e) {
System.out.println("Could not listen on port: 4444");
System.exit(-1);
}
// 2. LOOP FOREVER - SERVER IS ALWAYS WAITING TO PROVIDE SERVICE!
while (true) {
Socket clientSocket = null;
try {
// 2.1 WAIT FOR CLIENT TO TRY TO CONNECT TO SERVER
System.out.println("Waiting for client " + clientNum + " to connect!");
clientSocket = serverSocket.accept();
clientNum++;
ClientHandler c = new ClientHandler(clientSocket, clients);
clients.add(c);
// 2.2 SPAWN A THREAD TO HANDLE CLIENT REQUEST
Thread t = new Thread(c);
t.start();
} catch (IOException e) {
System.out.println("Accept failed: 4444");
System.exit(-1);
}
// 2.3 GO BACK TO WAITING FOR OTHER CLIENTS
// (While the thread that was created handles the connected client's
// request)
} // end while loop
} // end of main method
} // end of class MyServer
class ClientHandler implements Runnable {
Socket s; // this is socket on the server side that connects to the CLIENT
ArrayList<ClientHandler> others;
Scanner in;
PrintWriter out;
ClientHandler(Socket s, ArrayList<ClientHandler> others) throws IOException {
this.s = s;
this.others = others;
in = new Scanner(s.getInputStream());
out = new PrintWriter(s.getOutputStream());
}
/*
* (non-Javadoc)
*
* #see java.lang.Runnable#run()
*/
public void run() {
// 1. USE THE SOCKET TO READ WHAT THE CLIENT IS SENDING
while (true) {
String clientMessage = in.nextLine();
// System.out.println(clientMessage);
new Thread(new Runnable() {
#Override
public void run() {
try (PrintWriter fileWriter = new PrintWriter(new FileOutputStream(new File("chat.txt"), true));) {
fileWriter.println(clientMessage);
fileWriter.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// System.out.println(others.size());
for (ClientHandler c : others) {
// System.out.println(c.toString());
c.sendMessage(clientMessage);
}
}
}).start();
}
}
private void sendMessage(String str) {
out.println(str);
out.flush();
}
} // end of class ClientHandler
ClientSide.java
package core;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.BoxLayout;
import javax.swing.JTextArea;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
public class ClientSide extends JFrame {
private JPanel contentPane;
private JTextField textField;
private String name;
private JTextArea textArea;
private Thread serverListener;
private Socket socket;
private Scanner in;
private PrintWriter out;
// /**
// * Launch the application.
// */
// public static void main(String[] args) {
// EventQueue.invokeLater(new Runnable() {
// public void run() {
// try {
// ClientSide frame = new ClientSide();
// frame.setVisible(true);
// } catch (Exception e) {
// e.printStackTrace();
// }
// }
// });
// }
/**
* Create the frame.
*
* #throws IOException
*/
public ClientSide(String myName) {
try {
socket = new Socket("localhost", 4444);
in = new Scanner(socket.getInputStream());
out = new PrintWriter(socket.getOutputStream());
} catch (IOException e1) {
e1.printStackTrace();
}
serverListener = new Thread(new Runnable() {
#Override
public void run() {
while (true) {
String clientMessage = in.nextLine();
try {
System.out.println("Receiving before dec: " + clientMessage);
clientMessage = Crypto.decrypt(clientMessage, "key");
System.out.println("Receiving after dec: " + clientMessage);
addLine(clientMessage);
} catch (Exception e) {
e.printStackTrace();
}
}
}
});
serverListener.start();
name = myName;
setTitle("Client Side");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS));
JPanel topPanel = new JPanel();
FlowLayout flowLayout = (FlowLayout) topPanel.getLayout();
flowLayout.setAlignment(FlowLayout.LEFT);
contentPane.add(topPanel);
textArea = new JTextArea();
textArea.setEditable(false);
textArea.setColumns(20);
textArea.setRows(7);
topPanel.add(textArea);
JPanel bottomPanel = new JPanel();
contentPane.add(bottomPanel);
bottomPanel.setLayout(new FlowLayout(FlowLayout.LEFT, 5, 5));
JLabel lblMessage = new JLabel("Message");
bottomPanel.add(lblMessage);
textField = new JTextField();
bottomPanel.add(textField);
textField.setColumns(10);
JButton btnSend = new JButton("Send");
btnSend.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// send string/message to server
String clientMessage;
try {
clientMessage = Crypto.encrypt(name + ": > " + textField.getText(), "key");
System.out.println("Sending: " + clientMessage);
out.println(clientMessage);
out.flush();
} catch (Exception e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
});
bottomPanel.add(btnSend);
}
public void addLine(String text) {
textArea.setText(textArea.getText() + text + "\n");
}
}

Provided your ClientSide class connects with your server applicztion on port 4444, you can do the following:
Package your client as jar file and run on each computer you want to distribute it to.
Ensure, each of those computers have JRE installed.
3 Package your Server module as jar file
You should own your server or have admin right. So you can install Java if not there.
Depending on OS, SSH skill might be required
Ensure PORT 4444 is enabled on your host server. firewall
Get the public IP address of your server and use it in your ClideSide code.

simple client server chat application not working

I am trying to a simple client server chat application using Stream sockets and Swing. But it is not working as it should. Apparently the server just waits for connection and does not proceed.
I have three java files, Server.java , Client.java and ChatApp.java
Server.java
package com.htpj.networkingChatApp;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
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 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 static final long serialVersionUID = 1L;
private JTextArea displayArea;
private JTextField messageEnterField;
private ServerSocket server;
private Socket connectionSocket;
private ObjectInputStream input;
private ObjectOutputStream output;
private int counter = 1;
protected void serverGui() {
messageEnterField = new JTextField();
setMessageEnterFieldEditable(false);
messageEnterField.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
sendDataToClient(e.getActionCommand());
}
});
add(messageEnterField, BorderLayout.SOUTH);
displayArea = new JTextArea();
add(new JScrollPane(displayArea), BorderLayout.CENTER);
displayArea.setEditable(false); // display area is never editable
setSize(500, 500);
setLocationRelativeTo(null);
setTitle("Chat Server");
setVisible(true);
}
protected void runServer() {
try {
server = new ServerSocket(2000, 100);
while (true) {
try {
waitForConnection(); // wait for a connection
getStreams(); // get input and output streams
processConnection(); // process connections
} catch (EOFException e) {
displayMessage("\n server terminated the connection");
} finally {
closeConnection();
++counter;
}
}
} catch (IOException e) {
e.printStackTrace();
}
} // ENDOF method runServer
private void waitForConnection() {
try {
displayMessage("Waiting for Connection\n");
connectionSocket = server.accept();
displayMessage("Connection" + counter + "received from: " + connectionSocket.getInetAddress() + "port: "
+ connectionSocket.getPort());
} catch (IOException e) {
e.printStackTrace();
}
} // ENDOF method waitForConnection
private void getStreams() throws IOException {
output = new ObjectOutputStream(connectionSocket.getOutputStream());
output.flush(); // flush output buffer to send header information
input = new ObjectInputStream(connectionSocket.getInputStream());
displayMessage("\n Got I/O Streams \n");
} // ENDOF getStreams method
private void processConnection() throws IOException {
String message = null;
sendDataToClient("Connection Successful \n");
setMessageEnterFieldEditable(true); // enable server to type message
do {
try {
message = (String) input.readObject();
displayMessage("\n" + message);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
} while (!message.equals("CLIENT >> TERMINATE"));
} // ENDOF processConnection method
private void closeConnection() {
displayMessage("\n closing connection \n");
setMessageEnterFieldEditable(false);
try {
output.close();
input.close();
connectionSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
} // ENDOF closeConnection method
private void sendDataToClient(String messageFromServer) {
try {
output.writeObject("SERVER>> " + messageFromServer);
output.flush(); // flush output to client
} catch (IOException e) {
e.printStackTrace();
}
} // ENDOF sendDataToClient method
private void displayMessage(String showMessage) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
displayArea.append(showMessage);
}
});
} // ENDOF method displayMessage
private void setMessageEnterFieldEditable(final boolean isEditable) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
messageEnterField.setEditable(isEditable);
}
});
}
} // ENDOF class server
Client.java
package com.htpj.networkingChatApp;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
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.net.UnknownHostException;
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 static final long serialVersionUID = 1L;
private JTextField messageEnterField;
private JTextArea displayArea;
private String chatHost;
private Socket clientSocket;
private ObjectInputStream input;
private ObjectOutputStream output;
private String message = "";
public Client(String host) {
this.chatHost = host;
}
protected void clientGui() {
messageEnterField = new JTextField();
setMessageEnterFieldEditable(false);
messageEnterField.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
sendDataToServer(e.getActionCommand());
}
});
add(messageEnterField, BorderLayout.SOUTH);
displayArea = new JTextArea();
add(new JScrollPane(displayArea), BorderLayout.CENTER);
displayArea.setEditable(false);
setTitle("Chat Client");
setSize(500, 500);
setLocationRelativeTo(null);
setVisible(true);
} // END OF clientGui method
// connect to the server and process message from server
protected void runClient() throws UnknownHostException, IOException, ClassNotFoundException {
// connect to server, get Streams, process connection
try {
connectToServer();
getStreams();
processConnection();
} catch (EOFException e) {
displayMessage("\n client closed the connection");
} finally {
closeConnection();
}
}
private void connectToServer() throws UnknownHostException, IOException {
displayMessage("Attempting Connection to Server: \n");
clientSocket = new Socket(InetAddress.getByName(chatHost), 2000);
displayMessage(
"Connected to: " + clientSocket.getInetAddress().getHostName() + "on Port : " + clientSocket.getPort());
} // END OF method connectToServer
private void getStreams() throws IOException {
output = new ObjectOutputStream(clientSocket.getOutputStream());
output.flush();
input = new ObjectInputStream(clientSocket.getInputStream());
displayMessage("\n Got I/O stream \n ");
} // END OF getStreams method
private void processConnection() throws ClassNotFoundException, IOException {
displayMessage("\n connected to server\n");
setMessageEnterFieldEditable(true);
do {
message = (String) input.readObject();
displayMessage("\n" + message);
} while (!message.equals("SERVER>> TERMINATE"));
} // end of processConnection method
private void closeConnection() throws IOException {
displayMessage("\n closing connection ");
input.close();
output.close();
clientSocket.close();
setMessageEnterFieldEditable(false);
} // end of closeConnection method
private void displayMessage(final String messageToShow) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
displayArea.append(messageToShow);
}
});
} // end of displayMessage method
private void sendDataToServer(String messageToServer) {
try {
output.writeObject(messageToServer);
output.flush();
} catch (IOException e) {
e.printStackTrace();
}
} // end of sendDataToServer method
private void setMessageEnterFieldEditable(final boolean isEditable) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
messageEnterField.setEditable(isEditable);
}
});
}
}
ChatApp.java
package com.htpj.networkingChatApp;
import java.io.IOException;
public class ChatApp{
public static void main(String[] args) {
Server chatServer = new Server();
Client chatClient = new Client("127.0.0.1");
chatServer.serverGui();
chatClient.clientGui();
chatServer.runServer();
try {
chatClient.runClient();
} catch (ClassNotFoundException | IOException e) {
e.printStackTrace();
}
}
}

Java socket: how the server can reads multiple lines from the client

I create chat app one to one by using Java programming language
I faced issue: client can't send a new message until he receives a message from the server.

You should have a multithreaded application.
The client will run 2 threads:
1) Sender thread which will run on send button. You can every time create a new instance of this thread on clicking send button.
2) The receiver thread will keep on running continuously and check the stream for any message. Once it gets a message on stream it will write the same on console.
Will update you shortly with the code.
Thanks
Written this code long back similarly you can write server using other port
package com.clients;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class ClientFullDuplex extends JFrame implements ActionListener {
private JFrame jframe;
private JPanel jp1, jp2;
private JScrollPane jsp;
private JTextArea jta;
private JTextField jtf;
private JButton send;
private Thread senderthread;
private Thread recieverthread;
private Socket ds;
private boolean sendflag;
public static void main(String[] args) {
try {
ClientFullDuplex sfd = new ClientFullDuplex();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public ClientFullDuplex() throws UnknownHostException, IOException {
initGUI();
ds = new Socket("127.0.0.1", 1124);
initNetworking();
}
public void initGUI() {
jframe = new JFrame();
jframe.setTitle("Client");
jframe.setSize(400, 400);
jp1 = new JPanel();
jta = new JTextArea();
jsp = new JScrollPane(jta);
jtf = new JTextField();
send = new JButton("Send");
send.addActionListener(this);
jp1.setLayout(new GridLayout(1, 2, 10, 10));
jp1.add(jtf);
jp1.add(send);
jframe.add(jp1, BorderLayout.SOUTH);
jframe.add(jsp, BorderLayout.CENTER);
jframe.setVisible(true);
jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jta.append("hello client");
}
#Override
public synchronized void addWindowListener(WindowListener arg0) {
// TODO Auto-generated method stub
super.addWindowListener(arg0);
new WindowAdapter() {
#Override
public void windowClosing(WindowEvent arg0) {
// TODO Auto-generated method stub
if (ds != null)
try {
ds.close();
System.exit(0);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
}
public void initNetworking() {
try {
recieverthread = new Thread(r1);
recieverthread.start();
} catch (Exception e) {
e.printStackTrace();
}
}
Runnable r1 = new Runnable() {
#Override
public void run() {
try {
System.out.println(Thread.currentThread().getName()
+ "Reciver Thread Started");
recieveMessage(ds);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Runnable r2 = new Runnable() {
#Override
public void run() {
try {
System.out.println(Thread.currentThread().getName()
+ "Sender Thread Started");
sendMessage(ds);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
public void recieveMessage(Socket rms) throws IOException {
while (true) {
System.out.println(Thread.currentThread().getName()
+ "Reciver Functionality");
BufferedReader br = new BufferedReader(new InputStreamReader(
rms.getInputStream()));
String line = br.readLine();
System.out.println(line);
jta.append("\nServer:"+line);
}
}
public void sendMessage(Socket sms) throws IOException {
System.out.println(Thread.currentThread().getName()
+ "Sender Functionality");
PrintWriter pw = new PrintWriter(sms.getOutputStream(), true);
String sline = jtf.getText();
System.out.println(sline);
pw.println(sline);
jtf.setText("");
}
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if (e.getSource() == send) {
senderthread = new Thread(r2);
senderthread.start();
}
}
}

This is the code I copied and edited from your earlier post.
The problem is that the input stream from socket is blocking. So my suggestion is to read up on async sockets in java and refactor the code below.
next to that it isn't that difficult to edit posts.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Server {
public static void main(String[] args) {
Server chatServer = new Server(5555);
System.out.println("###Start listening...###");
chatServer.startListening();
chatServer.acceptClientRequest();
}
private ServerSocket listeningSocket;
private Socket serviceSocket;
private int TCPListeningPort;
private ArrayList<SocketHanding> connectedSocket;
public Server(int TCPListeningPort)
{
this.TCPListeningPort = TCPListeningPort;
connectedSocket = new ArrayList<SocketHanding>();
}
public void startListening()
{
try
{
listeningSocket = new ServerSocket(TCPListeningPort);
}
catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
public void acceptClientRequest()
{
try
{
while (true)
{
serviceSocket = listeningSocket.accept();
SocketHanding _socketHandling = new SocketHanding(serviceSocket);
connectedSocket.add(_socketHandling);
Thread t = new Thread(_socketHandling);
t.start();
System.out.println("###Client connected...### " + serviceSocket.getInetAddress().toString() );
}
}
catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
class SocketHanding implements Runnable
{
private Socket _connectedSocket;
private PrintWriter socketOut;
private InputStream socketIn;
private boolean threadRunning = true;
private String rmsg;
public SocketHanding(Socket connectedSocket) throws IOException
{
_connectedSocket = connectedSocket;
socketOut = new PrintWriter(_connectedSocket.getOutputStream(), true);
socketIn = _connectedSocket.getInputStream();
}
private void closeConnection() throws IOException
{
threadRunning = false;
socketIn.close();
socketOut.close();
_connectedSocket.close();
}
public void sendMessage(String message)
{
socketOut.println(message);
}
private String receiveMessage() throws IOException
{
String t = "";
if (_connectedSocket.getInputStream().available() > 0)
{
byte[] b = new byte[8192];
StringBuilder builder = new StringBuilder();
int bytesRead = 0;
if ( (bytesRead = _connectedSocket.getInputStream().read(b)) > -1 )
{
builder.append(new String(b, 0, b.length).trim());
}
t = builder.toString();
}
return t;
}
#Override
public void run()
{
while (threadRunning)
{
try
{
rmsg = receiveMessage();
System.out.println(rmsg);
if(rmsg.equalsIgnoreCase("bye"))
{
System.out.println("###...Done###");
closeConnection();
break;
}
else
{
String smsg = "";
BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
smsg = keyboard.readLine();
keyboard.close();
sendMessage("Server: "+smsg);
}
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}

Chat program freezes JFrame

I'm writing a simply chat client and am moving it over to a nice GUI. The constructor for the server side (client side is android) contains a list that's in the JFrame, and the first part of the server runs, but then the entire frame locks up. Does anyone see the issue? Sorry for the relatively disorganized, not cleanly commented code...
Server:
import java.awt.List;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.net.UnknownHostException;
public class ChatServer {
private final int CHAT_PORT = 4453;
ServerSocket sSocket;
Socket cSocket;
PrintWriter pWriter;
BufferedReader bReader;
InetAddress localAddr;
List messageList;
public ChatServer(List entList)
{
messageList = entList;
}
public synchronized void run()
{
messageList.add("Chat Server Starting...");
try {
localAddr = InetAddress.getLocalHost();
} catch (UnknownHostException e1) {
messageList.add("InnetAddress error");
}
while(true)
{
try {
sSocket = new ServerSocket(CHAT_PORT);
sSocket.setReuseAddress(true);
messageList.add("Server has IP:" + localAddr.getHostAddress());
messageList.add("Server has hostname:" + localAddr.getHostName());
messageList.add("Server has port:" + CHAT_PORT);
} catch (IOException e) {
//ERRORS
if(cSocket.isConnected())
{
messageList.add("User disconnected\n");
try {
cSocket.close();
} catch (IOException e1) {
messageList.add("Error closing client socket");
}
}
else
{
messageList.add("ERROR CREATING SOCKET\n");
}
}
try {
cSocket = sSocket.accept();
cSocket.setReuseAddress(true);
messageList.add("INFO: socket connected");
} catch (IOException e) {
messageList.add("Client Socket Error");
System.exit(-1);
}
try {
pWriter = new PrintWriter(cSocket.getOutputStream(), true);
messageList.add("INFO: Print writer opened");
} catch (IOException e) {
messageList.add("PrintWriter error");
}
try {
bReader = new BufferedReader(new InputStreamReader(cSocket.getInputStream()));
messageList.add("INFO: buffered reader opened");
} catch (IOException e) {
messageList.add("BufferedReader error");
}
String inputLine;
try {
while((inputLine = bReader.readLine()) != null)
{
messageList.add(inputLine);
if(inputLine.equals("close"))
{
close();
}
}
} catch (IOException e) {
messageList.add("Buffered Reader error");
}
}
}
public synchronized void close()
{
messageList.add("****Server closing****");
try {
sSocket.close();
} catch (IOException e) {
messageList.add("Error closing server socket");
}
try {
cSocket.close();
} catch (IOException e) {
messageList.add("Error closing client socket");
}
pWriter.close();
try {
bReader.close();
} catch (IOException e) {
messageList.add("Error closing buffered reader");
}
messageList.add("****It's been fun, but I've got to go.****\n****Server has shut down.****");
System.exit(0);
}
}
GUI:
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JMenu;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.List;
import java.awt.Toolkit;
#SuppressWarnings("serial")
public class ClientGUI extends JFrame {
private JPanel contentPane;
private JTextField txtEnterTextHere;
private JMenuBar menuBar;
private List messageList;
private JMenu mnOptions;
private JMenu mnHelp;
private JMenuItem mntmStartServer;
private JMenuItem mntmStopServer;
private JMenuItem mntmConnectionInfo;
private JMenuItem mntmEmailDeveloper;
private static String userName;
private ChatServer cServer;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
ClientGUI frame = new ClientGUI();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public ClientGUI() {
setTitle("Ben's Chat Client");
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
menuBar = new JMenuBar();
setJMenuBar(menuBar);
JMenu mnFile = new JMenu("File");
menuBar.add(mnFile);
JMenuItem mntmExit = new JMenuItem("Exit");
mntmExit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
JOptionPane.showConfirmDialog(null, "Are you sure you want to exit?");
}
});
mnFile.add(mntmExit);
mnOptions = new JMenu("Options");
menuBar.add(mnOptions);
mntmStartServer = new JMenuItem("Start Server");
mntmStartServer.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
ChatServer cServer = new ChatServer(messageList);
cServer.run();
}
});
mnOptions.add(mntmStartServer);
mntmStopServer = new JMenuItem("Stop Server");
mnOptions.add(mntmStopServer);
mntmConnectionInfo = new JMenuItem("Connection Info");
mnOptions.add(mntmConnectionInfo);
mnHelp = new JMenu("Help");
menuBar.add(mnHelp);
mntmEmailDeveloper = new JMenuItem("Email Developer");
mnHelp.add(mntmEmailDeveloper);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
txtEnterTextHere = new JTextField();
txtEnterTextHere.setBounds(10, 220, 334, 20);
txtEnterTextHere.setText("Enter text here...");
contentPane.add(txtEnterTextHere);
txtEnterTextHere.setColumns(10);
JButton btnSend = new JButton("Send");
btnSend.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
messageList.add(userName + ": " + txtEnterTextHere.getText().toString());
}
});
messageList = new List();
btnSend.setBounds(349, 219, 85, 23);
contentPane.add(btnSend);
messageList.setBounds(10, 10, 424, 204);
contentPane.add(messageList);
}
public static String getUsername()
{
return userName;
}
public static void setUsername(String entName)
{
userName = entName;
}
}
Thanks!

It looks like you're starting the server on the Swing thread (see: The Event Dispatch Thread). As soon as you call cServer.run(); in the ActionListener, you are blocking the EDT from doing anything else (such as updating your JFrame and responding to events). Start your server in a background thread instead:
new Thread(new Runnable()
{
#Override
public void run()
{
// start your server
}
}).start();

java.io.BufferedReader.readLine() is nonblocking

I have a problem with readLine() in Java. I have a server and a client. From client I want to send a message to the server. The problem is that first, the client has to insert a text into a JTextField and when presses send then server to read the input from client, but server doesn't wait the input from client but instead reads null. But I read that readLine() is blocked until it has something to read, why it's not happening in this case?
Here I connect to the server and create the JFrame
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class StartingPoint {
private static PrintWriter out;
private static BufferedReader in;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
try {
connectToServer();
createAndShowGui();
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
public static void createAndShowGui() throws IOException {
View frame = new View(out, in);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void connectToServer() throws IOException {
String serverAddress = "127.0.0.1";
int PORT = 8100;
Socket clientSocket = null;
out = null;
in = null;
try {
clientSocket = new Socket(serverAddress, PORT);
out = new PrintWriter(clientSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Could not connect to the server \n" + e);
System.exit(1);
} finally {
if (out != null)
out.close();
if (in != null)
in.close();
if (clientSocket != null)
clientSocket.close();
}
}
}
Here is JFrame implementation:
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class View extends JFrame {
private JButton button;
private JTextField field;
private JPanel gui;
public View(final PrintWriter out, final BufferedReader in) throws IOException {
button = new JButton("Send");
field = new JTextField();
gui = new JPanel(new GridLayout(1, 0, 10, 10));
gui.add(button);
gui.add(field);
add(gui);
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
out.println(field.getText());
try {
System.out.println(in.readLine());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
}
Here is the server:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class SimpleServer extends Thread {
public static final int PORT = 8100;
private static ServerSocket serverSocket = null;
private Socket clientSocket = null;
public void run() {
String receive, answer;
try {
BufferedReader in = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
PrintWriter out = new PrintWriter(clientSocket.getOutputStream());
receive = in.readLine();
System.out.println("[server]" + receive);
answer = "hello " + receive;
out.println(answer);
out.flush();
} catch (IOException e) {
System.err.println("IO error \n" + e);
} finally {
try {
clientSocket.close();
} catch (IOException e) {
System.err.println("Close socket error \n" + e);
}
}
}
public SimpleServer() throws IOException {
while (true) {
serverSocket = new ServerSocket(PORT);
try {
clientSocket = serverSocket.accept();
new Thread(this).start();
} finally {
serverSocket.close();
}
}
}
public static void main(String[] args) throws IOException {
SimpleServer server = new SimpleServer();
}
}

Your connectToServer() method opens a connection, creates streams and ... then closes them before returning. So of course, the server sees the close straight away, and returns null on the first readLine() call.
I suspect that you may have copied the "close in a finally block" pattern without understanding what it means. So I shall explain:
This is the normal pattern:
InputStream is = null;
try {
is = new FileInputStream(someFile);
// read the stream
} finally {
if (is != null) {
is.close();
}
}
The purpose of the code above is to ensure that the InputStream is always closed. Or more precisely, that it is always closed before the try/finally exits.
This is generally a good thing. But if the purpose of your code is to open some streams that is going to be used after this bit of code completes, then closing the stream here is self defeating.
InputStream is = null;
try {
is = new FileInputStream(someFile);
} finally {
if (is != null) {
is.close();
}
}
// read the stream ... OOOPS! We've already closed it!!
So to take this back to your original code, you need to move the try/finally/close stuff to the run method, something along these lines:
public void run() {
try {
connectToServer();
createAndShowGui();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (out != null)
out.close();
if (in != null)
in.close();
if (clientSocket != null)
clientSocket.close();
}
}
You should also catch and (probably) ignore IOException that might be thrown by each close() call.

Javadoc for BufferedReader.readLine()
doesn't say anything like that:
Returns:
A String containing the contents of the line, not including
any line-termination characters, or null if the end of the stream has been reached
In your code you are opening a connection in connectToServer() and closing it, so server sees the end of stream