import java.net.*;
import java.io.*;
import java.util.*;
public class chatserver
{
	public static void main(String[] args) throws IOException
	{
			ServerSocket socket=null;
			Vector m_threads=new Vector();
			System.out.println("Listen...");
			try
			{
				socket=new ServerSocket(5555);
			}
			catch(Exception e)
			{
				System.out.println("new ServerSocket() failed!");
				return;	
			}
			try
			{
				int nid=0;
				while(true)
				{
					//監聽是否有新chat Applet連接到Server,
					//程序會陷入到該語句，直到有新的連接產生。
					Socket s=socket.accept();
					System.out.println("accepted");
					//創建一個新的ServerThread
					ServerThread st=new ServerThread(s,m_threads);
					//為該線程設置一個ID號。
					st.setID(nid++);
					//將該線程加入到m_threads Vector中。
					m_threads.addElement(st);
					new Thread(st).start();
					//通知所有Chat Applet有一個新的網友加入
					for(int i=0;i<m_threads.size();i++)
					{
						ServerThread st1=(ServerThread)m_threads.elementAt(i);
						st1.write("<#>welcome"+st.getID()+"to enter chatroom!");
					}
					System.out.println("Listen again...");
						
				}		
			}
			catch(Exception e)
			{
				System.out.println("Server is down...");	
			}
	}		
}
/*
 *ServerThread是監聽線程，用于監聽對應的Chat Applet是否有信息傳來。
*/
class ServerThread implements Runnable
{
	Vector m_threads;
	Socket m_socket=null;
	DataInputStream m_in=null;
	DataOutputStream m_out=null;
	
	int m_nid;
	//初始化該線程
	public ServerThread(Socket s,Vector threads)
	{
		m_socket=s;
		m_threads=threads;
		try
		{
	//		System.out.println(inetaddr);
			m_in=new DataInputStream(m_socket.getInputStream());
			m_out=new DataOutputStream(m_socket.getOutputStream());
		}
		catch(Exception e)
		{
				
		}	
		
	}
	//線程的執行體
	public void run()
	{
		System.out.println("Thread is runing");
		try
		{
			while(true)
			{
				//監聽對應的Applet是否傳來消息
				//程序陷入到m_in.readUTF()中，直到有信息傳來才返回。
				String s=m_in.readUTF();
				if(s==null)
				 	break;
				if(s.equals("leave"))
					for(int i=0;i<m_threads.size();i++)
					{
						ServerThread st=(ServerThread) m_threads.elementAt(i);
						st.write("***"+getID()+"leave..."+"***");
						m_threads.removeElement(this);		
					}
				else
				{
					for(int i=0;i<m_threads.size();i++)
					{
						ServerThread st=(ServerThread) m_threads.elementAt(i);
						st.write("<"+getID()+">"+s);
					}	
				}
				
			}	
		}
		catch(Exception e)
		{
			e.printStackTrace();	
		}
		//從m_threads Vector中刪除該線程，表示該線程已經離開chat room
		//m_threads.removeElement(this);
		try
		{
			m_socket.close();	
		}	
		catch(Exception e)
		{
			
		}
	}
	//write()將msg送回對應的Applet
	public void write(String msg)
	{
		synchronized(m_out)
		{
			try
			{
				m_out.writeUTF(msg);	
			}	
			catch(Exception e)
			{
				
			}
		}	
	}
	//獲得該線程的ID
	public int getID()
	{
		return m_nid;	
	}
	//設置線程的ID
	public void setID(int nid)
	{
		m_nid=nid;
	}
}