About this question
In an attempt to learn more with Java, I decided to challenge myself by creating a GUI-based, multi-threaded chat room. Currently, you run the Client and it prompts you to either create or join a server based on an IP. Port used is 9000. Any suggestions on how I can improve?
Server.java:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.sql.Timestamp;
import java.util.HashSet;
import java.util.Set;
public class Server extends Thread {
/**
* Used to write to all the connected clients.
*/
private static final SetWRITERS = new HashSet<>();
/**
* Used to keep track of all of the names of connected clients.
*/
private static final SetNAMES = new HashSet<>();
/**
* Used to keep track of the current client's ID for logging purposes.
*/
private static int clientId = 1;
/**
* Used when creating a server.
*/
private final ServerSocket listener;
public Server(ServerSocket listener) {
this.listener = listener;
}
/**
* Used to log messages.
*
* @param message
*/
public static void log(String message) {
String timestamp = new Timestamp(System.currentTimeMillis()).toString();
timestamp = timestamp.substring(0, timestamp.length() - 4);
System.out.println("[" + timestamp + "] " + message);
}
/**
* Returns the ServerSocket listener.
*
* @return
*/
public ServerSocket getListener() {
return this.listener;
}
@Override
public void run() {
if (listener != null) {
try {
if (listener.isBound()) {
log("Server started on " + (listener.getInetAddress().getHostAddress()) + " and listening on port "
+ ServerConstants.PORT);
}
while (true) {
new User(listener.accept(), clientId++).start();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
listener.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/**
* Creates a server and starts accepting inputs.
*
* @param port
* @throws IOException
*/
public static Server createServer(int port) throws IOException {
return new Server(new ServerSocket(port));
}
/**
* This class listens for and sends messages to messages from all clients.
*
* @author ivisc
*
*/
private static class User extends Thread {
private Socket socket;
private PrintWriter out;
private BufferedReader in;
private String address;
private String name;
private int id;
public User(Socket sock, int id) {
this.socket = sock;
this.id = id;
this.address = socket.getInetAddress().getHostAddress();
}
@Override
public void run() {
try {
log("Starting connection from " + this.toString());
// Start up our variables for use with the socket.
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
// Ask for a name
while (true) {
out.println("ENTERNAME");
String line = in.readLine();
if (line == null) {
return;
}
if (!Filter.filter(line)) {
out.println("INVALIDNAME");
} else {
synchronised (NAMES) {
if (!NAMES.contains(line)) {
NAMES.add(line);
name = line;
out.println("NAME ACC");
break;
}
}
}
}
WRITERS.add(out);
log("Registering " + this.toString() + " (" + name + ")");
for (PrintWriter writer : WRITERS) {
writer.println("NEWMEM" + name);
}
// Now we listen for names
while (true) {
String message = in.readLine();
if (message == null) {
return;
}
if (!Filter.filter(message)) {
out.println("INVALIDMESSAGE");
} else {
for (PrintWriter writer : WRITERS) {
writer.println("MESSAGE" + name + ": " + message);
}
}
}
} catch (IOException e) {
log(this.toString() + " is disconnecting...");
} finally {
log("Shutting down I/O from " + this.toString() + " (" + id + ")");
try {
out.close();
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
@Override
public String toString() {
return address + "(" + id + ")";
}
}
}
Client.java:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
@SuppressWarnings("serial")
public class Client extends JFrame {
private JTextField textField;
private JTextArea textArea;
private Socket socket;
private PrintWriter out;
private BufferedReader in;
public Client() {
textField = new JTextField(40);
getContentPane().add(textField, BorderLayout.SOUTH);
textField.setEditable(false);
textArea = new JTextArea();
getContentPane().add(textArea, BorderLayout.NORTH);
textArea.setEditable(false);
getContentPane().add(new JScrollPane(textArea), BorderLayout.CENTER);
textField.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
out.println(textField.getText());
textField.setText("");
}
});
setPreferredSize(new Dimension(800, 600));
pack();
setSize(getPreferredSize());
setLocationRelativeTo(null);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void initVars() throws IOException {
this.out = new PrintWriter(socket.getOutputStream(), true);
this.in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
}
public void connect(String address) {
try {
this.socket = new Socket(address, ServerConstants.PORT);
initVars();
this.textField.setEditable(true);
Server.log("Connected to " + address);
this.setVisible(true);
while (true) {
new ServerListener(out, in).start();
}
} catch (IOException e) {
e.printStackTrace();
}
}
public void connect(Server server) {
try {
String address = server.getListener().getInetAddress().getHostAddress();
this.socket = new Socket(address, ServerConstants.PORT);
initVars();
this.textField.setEditable(true);
Server.log("Connected to " + address);
this.setVisible(true);
while (true) {
new ServerListener(out, in).start();
}
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
Object[] options = new Object[] { "Start", "Join", "Cancel" };
int input = JOptionPane.showOptionDialog(null, "Would you like to create or join a server?",
"Chat Room Selection", JOptionPane.YES_NO_CANCEL_OPTION, JOptionPane.INFORMATION_MESSAGE, null, options,
options[1]);
Client client = new Client();
switch (input) {
case 0:
try {
Server server = Server.createServer(ServerConstants.PORT);
server.start();
client.connect(server);
} catch (IOException e) {
e.printStackTrace();
}
break;
case 1:
String address = JOptionPane.showInputDialog("Please enter server IP");
if (address != null) {
client.connect(address);
}
break;
case 2:
System.exit(0);
break;
}
s.close();
}
private class ServerListener extends Thread {
private PrintWriter out;
private BufferedReader in;
public ServerListener(PrintWriter out, BufferedReader in) {
this.out = out;
this.in = in;
}
@Override
public void run() {
while (true) {
try {
handle(in.readLine());
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void handle(String message) throws IOException {
System.out.println("handling " + message);
if (message == null) {
return;
}
System.out.println(message);
if (message.startsWith("MESSAGE")) {
message = message.substring(7);
textArea.append(message + "n");
} else if (message.startsWith("ENTERNAME")) {
while (true) {
String name = JOptionPane.showInputDialog("Please enter a username");
out.println(name);
String response = in.readLine();
if (response.equals("INVALIDNAME")) {
JOptionPane.showMessageDialog(null, "Name does not pass Name Filter", "Invalid Name",
JOptionPane.ERROR_MESSAGE);
} else {
break;
}
}
} else if (message.startsWith("NEWMEM")) {
String name = message.substring(6);
textArea.append(name + " has joined the server.n");
}
}
}
}
There are a few references to ServerConstants.java and Filter.java here, but I won't include them for brevity's sake. Basically, ServerConstants is an abstract interface that just defines the port to use, and Filter is a simple name filter using a list of "bad words" (I believe it's this one that I used).
I know I didn't comment on everything, and adding throws statements might not be best practice, and extending from JFrame is usually not recommended, but, based on everything here, any suggestions?
