怎样解决不能实例化？

[videostudent]

我写的一个多线程的socket通信，客户端程序run java applet总是说无法实例化，但是作为java appllication 是成功连接的，请问这是为什么？源程序如下：
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class Client extends Panel
{
//界面设计和添加事件响应
private TextField tf = new TextField();//文本输入框
private TextArea ta = new TextArea();//聊天记录窗口
private Socket socket;
private DataOutputStream dout;
private DataInputStream din;



public Client( String host, int port ) {

setLayout( new BorderLayout() );
add( "North", tf );
add( "Center", ta );

tf.addActionListener( new ActionListener() {
public void actionPerformed( ActionEvent e ) {
processMessage( e.getActionCommand() );
}
} );


//敲回车键以后，与服务器进行连接
try {

socket = new Socket( host, port );
System.out.println( "connected to "+socket );

din = new DataInputStream( socket.getInputStream() );
dout = new DataOutputStream( socket.getOutputStream() );
run();
// 启动一个消息接收的线程
// new Thread( this ).start();
} catch( IOException ie ) { System.out.println( ie ); }
}

// 接收键盘输入并发送消息
private void processMessage( String message ) {
try {
dout.writeUTF( message );

tf.setText( "" );
} catch( IOException ie ) { System.out.println( ie ); }
}

// 在另一个窗口显示聊天消息
public void run() {
try {
while (true) {

String message = din.readUTF();
ta.append( message+"\n" );
}
} catch( IOException ie ) { System.out.println( ie ); }
}

static public void main( String args[] ) throws Exception {
String host = "202.197.111.196" ;

int port=9000;

new Client( host, port ) ;

}
}

[videostudent]

这是提示信息：
载入：无法实例化 Client.class。
java.lang.InstantiationException: Client
at java.lang.Class.newInstance0(Class.java:281)
at java.lang.Class.newInstance(Class.java:249)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:548)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:477)
at sun.applet.AppletPanel.run(AppletPanel.java:290)
at java.lang.Thread.run(Thread.java:536)