IPV4 IPV6 数据成员

typedef uint16_t in_port_t;

// Internet address. --- IPV4
typedef uint32_t in_addr_t;
struct in_addr{
     in_addr_t s_addr;
};



// IPv6 address
struct in6_addr
{
	union
	{   
		uint8_t __u6_addr8[16];
	} __in6_u;
};  


// Structure describing an Internet socket address   --- IPV4
struct sockaddr_in
{
	__SOCKADDR_COMMON (sin_);
	in_port_t sin_port;         /* Port number.  */
	struct in_addr sin_addr;        /* Internet address.  */

	/* Pad to size of `struct sockaddr'.  */
	unsigned char sin_zero[sizeof (struct sockaddr) -
		__SOCKADDR_COMMON_SIZE -
		sizeof (in_port_t) -
		sizeof (struct in_addr)];
};


/* Ditto, for IPv6.  */
struct sockaddr_in6
{
	__SOCKADDR_COMMON (sin6_);
	in_port_t sin6_port;    /* Transport layer port # */
	uint32_t sin6_flowinfo; /* IPv6 flow information */
	struct in6_addr sin6_addr;  /* IPv6 address */
	uint32_t sin6_scope_id; /* IPv6 scope-id */
};

struct in_addr 仅一个成员， s_addr (uint32_t)
struct in6_addr 仅一个成员 __u6_addr ( uint8_t [16])

IPV4: socket_in 共4个成员：
	unsignedshort	sin_family	--> 协议族类型
	uint16_t  sin_port 		--> 端口号
	struct in_addr     sin_addr     --> ip地址
	unsigned   char sin_zero        --> 
IPV6: socket_in6 共4个成员：
	uint16_t sin6_port;   		/* Transport layer port # */
	uint32_t sin6_flowinfo; 	/* IPv6 flow information */
	struct in6_addr sin6_addr;	/* IPv6 address */
	uint32_t sin6_scope_id; 	/* IPv6 scope-id */

struct sockaddr{
　　unsignedshort sa_family; /* address family */ 
　　char sa_data[14]; /* up to 14 bytes of direct address */
};