UNP学习笔记（1）-Sockets Introduction：Socket Address Structure

1. 1、IPv4 Socket Address Structure

struct in_addr {

  in_addr_t   s_addr;           /* 32-bit IPv4 address */

                                /* network byte ordered */

};



struct sockaddr_in {

  uint8_t         sin_len;      /* length of structure (16) */

  sa_family_t     sin_family;   /* AF_INET */

  in_port_t       sin_port;     /* 16-bit TCP or UDP port number */

                                /* network byte ordered */

  struct in_addr  sin_addr;     /* 32-bit IPv4 address */

                                /* network byte ordered */

  char            sin_zero[8];  /* unused */

};

定义在：<netinet/in.h>

2、Generic Socket Address Structure

struct sockaddr {

  uint8_t      sa_len;

  sa_family_t  sa_family;    /* address family: AF_xxx value */

  char         sa_data[14];  /* protocol-specific address */

};

定义在：<sys/socket.h>

这个结构是通用的，符合ANSI C,所以socket函数都使用此结构作为参数进行传递。比如：

1. int bind(int, struct sockaddr *, socklen_t);
2. 故在使用IPv4 Socket Address Structure时，就会有以下的转换：

struct sockaddr_in  serv;      /* IPv4 socket address structure */



/* fill in serv{} */



bind(sockfd, (struct sockaddr *) &serv, sizeof(serv));

3、IPv6 Socket Address Structure

3. 
   

struct in6_addr {

  uint8_t  s6_addr[16];          /* 128-bit IPv6 address */

                                 /* network byte ordered */

};



#define SIN6_LEN      /* required for compile-time tests */



struct sockaddr_in6 {

  uint8_t         sin6_len;      /* length of this struct (28) */

  sa_family_t     sin6_family;   /* AF_INET6 */

  in_port_t       sin6_port;     /* transport layer port# */

                                 /* network byte ordered */

  uint32_t        sin6_flowinfo; /* flow information, undefined */

  struct in6_addr sin6_addr;     /* IPv6 address */

                                 /* network byte ordered */

  uint32_t        sin6_scope_id; /* set of interfaces for a scope */

};

4、New Generic Socket Address Structure

struct sockaddr_storage {

  uint8_t      ss_len;       /* length of this struct (implementation dependent) */

  sa_family_t  ss_family;    /* address family: AF_xxx value */

  /* implementation-dependent elements to provide:

   * a) alignment sufficient to fulfill the alignment requirements of

   *    all socket address types that the system supports.

   * b) enough storage to hold any type of socket address that the

   *    system supports.

   */

};