默认的socket选项不够用的时候，就必须要使用setsockopt来调整。就是使用setsockopt。
首先看一下socket的setsockopt 函数的定义：
- socket.setsockopt(level,optname, value)
-
Set the value of the given socket option (see the Unix manual pagesetsockopt(2)). The needed symbolic constants are defined in thesocket module (SO_* etc.). The value can be an integer or a string representing a buffer. In the latter case it is up to the caller to ensure that the string contains the proper bits (see the optional built-in modulestruct for a way to encode C structures as strings).
level：选项定义的层次。支持SOL_SOCKET、IPPROTO_TCP、IPPROTO_IP和IPPROTO_IPV6。
optname：需设置的选项。
value：设置选项的值。
