[해결] 자바 소켓 프로그래밍 질문입니다.

import java.io.*;
import java.net.*;
import java.util.*;
 
class BroadcastServer {
	final static int PORT = 8001;
	ServerSocket server = null;
	Vector clients = new Vector();
 
	class Client extends Thread {
		Socket socket = null;
		BufferedReader in = null;
		PrintWriter out = null;
 
		Client (Socket socket) throws IOException {
			this.socket = socket;
			this.in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			this.out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()), true);
			start();
		}
 
		public void run() {
			try {
				while (true) {
					String line = in.readLine();
					if (line == null) {
						close();
						break;
					}
 
					System.out.println(getName()+':'+line);
					BroadcastServer.this.broadcast(line);
				}
			} catch (IOException ie) {
				ie.printStackTrace();
				close();
			}
		}
 
		public void close() {
			synchronized (BroadcastServer.this) {
				try {
					if (in != null)
						in.close();
				} catch (Exception e) {}
				if (out != null)
					out.close();
				try {
					if (socket != null)
						socket.close();
				} catch (Exception e) {}
				socket = null;
			}
		}
	}
 
	public BroadcastServer() {
		try {
			server = new ServerSocket(PORT);
		} catch (IOException ie) {
			ie.printStackTrace();
			System.exit(1);
		}
		while (true) {
			try {
				Socket socket = server.accept();
				Client client = new Client(socket);
				synchronized (this) {
					clients.addElement(client);
				}
			} catch (IOException ie) {
				ie.printStackTrace();
			}
		}
	}
 
 
	public static void main(String[] args) {
		new BroadcastServer();
	}
 
	public synchronized void broadcast(String message) {
		for (Enumeration enuma = clients.elements(); enuma.hasMoreElements(); ) {
			Client client = (Client) enuma.nextElement();
			if (client == null)
				continue;
			if (client.socket == null) {
				clients.removeElement(client);
				continue;
			}
			client.out.println(message);
			if (client.out.checkError()) {
				System.err.println("Error while sending message.");
				client.close();
			}
		}
	}
}

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.net.*;
import java.io.*;
 
public class BroadcastApplet extends Applet implements ActionListener {
	int port;
	String host;
	TextField inputField;
	TextArea outputArea;
	Socket socket;
	BufferedReader in;
	PrintWriter out;
	Thread readingThread;
 
	public void init() {
		inputField = new TextField();
		outputArea = new TextArea();
		setLayout(new BorderLayout());
		add(inputField, "North");
		add(outputArea, "Center");
		String param = getParameter("PORT");
		if (param == null)
			port = 8001;
		else
			port = Integer.parseInt(param);
		host = getParameter("HOST");
		if (host == null)
			host = getCodeBase().getHost();
		inputField.addActionListener(this);
		doLayout();
	}
 
	public void start() {
		if (socket == null)
			connect();
		readingThread = new Thread() {
			public void run() {
				if (socket == null)
					return;
				while (socket != null && readingThread == Thread.currentThread()) {
					try {
						String line = in.readLine();
						appendLine(line);
					} catch (IOException ie) {
						ie.printStackTrace();
						closeSocket();
					}
				}
			}
		};
		readingThread.start();
	}
 
	public void stop() {
		readingThread = null;
		closeSocket();
	}
 
	public void actionPerformed(ActionEvent ae) {
		if (ae.getSource() instanceof TextField) {
			String line = inputField.getText();
			inputField.setText("");
			if (socket == null)
				return;
			try {
				out.println(line);
				if (out.checkError())
					throw new IOException("Print error");
			} catch (IOException ie) { 
				closeSocket();
			}
		}
	}
 
	public void connect() {
		try {
			socket = new Socket(host, port);
			in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
			out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()), true);
			appendLine("Connected...");
		} catch (UnknownHostException uhe) {
			appendLine("Unknown host");
		} catch (IOException ie) {
			ie.printStackTrace();
		}
	}
 
	public synchronized void closeSocket() {
		try {
			if (in != null)
				in.close();
		} catch (Exception e) {}
		if (out != null)
			out.close();
		try {
			if (socket != null)
				socket.close();
		} catch (Exception e) {
			socket = null;
		}
	}
 
	public synchronized void appendLine(String message) {
		outputArea.append(message+"\n");
	}
}

java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:8001 connect,resolve)
	at java.security.AccessControlContext.checkPermission(Unknown Source)
	at java.security.AccessController.checkPermission(Unknown Source)
	at java.lang.SecurityManager.checkPermission(Unknown Source)
	at java.lang.SecurityManager.checkConnect(Unknown Source)
	at sun.plugin2.applet.Applet2SecurityManager.checkConnect(Unknown Source)
	at java.net.Socket.connect(Unknown Source)
	at java.net.Socket.connect(Unknown Source)
	at java.net.Socket.<init>(Unknown Source)
	at java.net.Socket.<init>(Unknown Source)
	at BroadcastApplet.connect(BroadcastApplet.java:99)
	at BroadcastApplet.start(BroadcastApplet.java:54)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
예외: java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:8001 connect,resolve)