using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace centralController.WebServer
{
    class LazySingleton
    {
        private static TcpListener listener = null;
       
        private static readonly object syncRoot = new object();
        private LazySingleton()
        { 
        }
        public static TcpListener GetInstance(IPAddress localAddr,Int32 port)
        {
            //第一重判断，先判断实例是否存在，不存在再加锁处理  
            if (listener == null)
            {
                //加锁的程序在某一时刻只允许一个线程访问  
                lock (syncRoot)
                {
                    //第二重判断  
                    if (listener == null)
                    {
                        listener = new TcpListener(localAddr, port);  //创建单例实例  
                    }
                }
            }
            return listener;
        }  
    }
}