在控制台宿主程序中，为什么不能同时实例化两个ServiceHost？

Question

代码如下： 

using (ServiceHost 
                DuplexCommonHost = new ServiceHost(typeof(DuplexCommonService)), 
                OneWayCommonHost = new ServiceHost(typeof(OneWayCommonService)))
            {
                DuplexCommonHost.Opened += delegate { Console.Write("DuplexCommon service has been opened!"); };
                DuplexCommonHost.Open();

                OneWayCommonHost.Opened += delegate { Console.Write("OneWayCommon service has been opened!"); };
                OneWayCommonHost.Open();

                Console.Read();   
            }

结果客户端报一下错误：没有终结点在侦听可以接受消息的 http://localhost:8080/OneWayCommon

屏蔽红色部分代码，客户端正常运行。