synchronized void writeAll(String str) {	//ʹ׽Ϣ
		PrintWriter write=null;
		Socket socket;
		for(int i=0;i<size();i++) {
			socket=(Socket)get(i);	//	ȡ׽
			try {
				write=new PrintWriter(socket.getOutputStream(),true);	//	
				if(write != null)
					write.println(str);	//ͨϢ
			}catch(Exception e){
				e.printStackTrace();
			}
		}
	}