Windows Socket 编程
int recvfrom( _In_ SOCKET s, _Out_ char *buf, _In_ int len, _In_ int flags, _Out_ struct sockaddr *from, _Inout_opt_ int *fromlen );
需要牢牢记住的是:fromlen指向的是struct sockaddr的长度
int recvfrom( _In_ SOCKET s, _Out_ char *buf, _In_ int len, _In_ int flags, _Out_ struct sockaddr *from, _Inout_opt_ int *fromlen );
需要牢牢记住的是:fromlen指向的是struct sockaddr的长度