哟哟哟，JAVA组装的聊天室，最简单的实现

import java.io.*;
import java.net.*;
import java.util.*;

public class VerySimpleChatServer {

ArrayList  clientOutputStream;

public class ClientHandler implements Runnable {
BufferedReader reader;
Socket sock;
public ClientHandler(Socket clientSocket) {
try {
sock = clientSocket;
InputStreamReader isReader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(isReader);
} catch (Exception ex) {
ex.printStackTrace();
}
}

public void run() {
String message;
try {
while ((message = reader.readLine()) != null) {
System.out.println("read " + message);
tellEveryone(message);
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
new VerySimpleChatServer().go();
}
public void go() {
clientOutputStream = new ArrayList();
try {
ServerSocket serverSock = new ServerSocket(5000);

while(true) {
Socket clientSocket = serverSock.accept();
PrintWriter writer = new PrintWriter(clientSocket.getOutputStream());
clientOutputStream.add(writer);

Thread t = new Thread(new ClientHandler(clientSocket));
t.start();
System.out.println("service at port 5000...");
System.out.println("got a connection...");
}
} catch (Exception ex) {
ex.printStackTrace();
}
}

public void tellEveryone(String message) {

Iterator it = clientOutputStream.iterator();
while(it.hasNext()) {
try {
PrintWriter writer = (PrintWriter) it.next();
writer.println(message);
writer.flush();
} catch (Exception ex) {
ex.printStackTrace();
}
}

}

}

import java.io.*;
import java.net.*;
import java.util.*;

import javax.swing.*;

import java.awt.*;
import java.awt.event.*;

public class SimpleChatClient {

JTextArea incoming;
JTextField outgoing;
BufferedReader reader;
PrintWriter writer;
Socket sock;

public static void main(String[] args) {
// TODO Auto-generated method stub
SimpleChatClient client = new SimpleChatClient();
client.go();

}
public void go() {
JFrame frame = new JFrame("Ludicrously Simple Chat Client");
JPanel mainPanel = new JPanel();
incoming = new JTextArea(15, 30);
incoming.setLineWrap(true);
incoming.setWrapStyleWord(true);
incoming.setEditable(false);
JScrollPane qScroller = new JScrollPane(incoming);
qScroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
qScroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
outgoing= new JTextField(20);
JButton sendButton = new JButton("Send");
sendButton.addActionListener(new SendButtonListener());
mainPanel.add(qScroller);
mainPanel.add(outgoing);
mainPanel.add(sendButton);
setUpNetworking();

Thread readerThread = new Thread(new IncomingReader());
readerThread.start();

frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
frame.setSize(400, 500);
frame.setVisible(true);

}

private void setUpNetworking() {
try {
sock = new Socket("127.0.0.1", 5000);
InputStreamReader streamReader = new InputStreamReader(sock.getInputStream());
reader = new BufferedReader(streamReader);
writer = new PrintWriter(sock.getOutputStream());
System.out.println("networking established");

} catch (IOException ex) {
ex.printStackTrace();
}
}

public class SendButtonListener implements ActionListener {
public void actionPerformed(ActionEvent ev) {
try {
writer.println(outgoing.getText());
writer.flush();
} catch(Exception ex) {
ex.printStackTrace();
}
outgoing.setText("");
outgoing.requestDefaultFocus();
}
}
public class IncomingReader implements Runnable {
public void run() {
String message;
try {
while ((message = reader.readLine()) != null) {
System.out.println("read " + message);
incoming.append(message + "\n");
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}

}