The difference between struct sockaddr and struct sockaddr_in, struct sockaddr_un

In the Linux environment, the structure struct sockaddr is defined in/usr/include/linux/socket.h, as follows:

typedef unsigned short sa_family_t;

struct SOCKADDR {

sa_family_t sa_family; /* Address family, AF_XXX * *

Char sa_data[14]; * Bytes of protocol address * *

};

In the Linux environment, the structure struct sockaddr_in is defined in/usr/include/netinet/in.h, as follows:

/* Structure describing an Internet sockets address. */

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)];

/* character Array sin_zero[8] exists to ensure that the size of the structure struct sockaddr_in is equal to the size of the struct sockaddr of the structure body.

};

struct sockaddr is a generic socket address, and struct sockaddr_in is the address form of the socket in the Internet environment, which is 16 bytes in length. The two are parallel structures, and pointers to sockaddr_in structures can point to sockaddr. In general, you need to cast the SOCKADDR_IN structure into the SOCKADDR structure and then into the system call function.

The following two data types are used in the struct sockaddr_in, which are defined as follows:

/* Type to represent a port. */

typedef uint16_t IN_PORT_T;

struct IN_ADDR is actually a 32-bit IP address.

struct IN_ADDR {

unsigned long s_addr;

};