（基于select模型）socket的封装类【超详细注释】，可以直接来用，讨论下优劣.. 这是服务器端，我在VS2008编译过了.. -(Based on select models) socket wrappers】 【super-detailed notes, can be used directly to discuss the pros and cons .. it is under the server side, I have compiled a VS2008 ..