IPv4地址的结构体与网络字节序

/* Fixed-size types, underlying types depend on word size and compiler.  */
typedef signed char __int8_t;
typedef unsigned char __uint8_t;
typedef signed short int __int16_t;
typedef unsigned short int __uint16_t;
typedef signed int __int32_t;
typedef unsigned int __uint32_t;
#if __WORDSIZE == 64
typedef signed long int __int64_t;
typedef unsigned long int __uint64_t;
#else
__extension__ typedef signed long long int __int64_t;
__extension__ typedef unsigned long long int __uint64_t;
#endif


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


/* POSIX.1g specifies this type name for the `sa_family' member.  */
typedef unsigned short int sa_family_t;

/* This macro is used to declare the initial common members
   of the data types used for socket addresses, `struct sockaddr',
   `struct sockaddr_in', `struct sockaddr_un', etc.  */

#define	__SOCKADDR_COMMON(sa_prefix) \
  sa_family_t sa_prefix##family


/* Structure describing a generic socket address.  */
struct sockaddr
  {
    __SOCKADDR_COMMON (sa_);	/* Common data: address family and length.  */
    char sa_data[14];		/* Address data.  */
  };


/* Structure describing an Internet socket 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)];
  };

 Name         Purpose                                    Man page
 AF_UNIX      Local communication                        unix(7)
 AF_LOCAL     Synonym for AF_UNIX
 AF_INET      IPv4 Internet protocols                    ip(7)
 AF_IPX       IPX - Novell protocols
 AF_INET6     IPv6 Internet protocols                    ipv6(7)
 AF_PACKET    Low-level packet interface                 packet(7)

/* Internet address.  */
typedef unsigned int __uint32_t;

typedef uint32_t in_addr_t;
struct in_addr
  {
    in_addr_t s_addr;
  };

/* POSIX.1g specifies this type name for the `sa_family' member.  */
typedef unsigned short int sa_family_t;

/* This macro is used to declare the initial common members
   of the data types used for socket addresses, `struct sockaddr',
   `struct sockaddr_in', `struct sockaddr_un', etc.  */

#define	__SOCKADDR_COMMON(sa_prefix) \
  sa_family_t sa_prefix##family

/* Structure describing a generic socket address.  */
struct sockaddr
  {
    __SOCKADDR_COMMON (sa_);	/* Common data: address family and length.  */
    char sa_data[14];		/* Address data.  */
  };

# define __CONST_SOCKADDR_ARG	const struct sockaddr *

/* Give the socket FD the local address ADDR (which is LEN bytes long).  */
extern int bind (int __fd, __CONST_SOCKADDR_ARG __addr, socklen_t __len)
     __THROW;

if (bind(listenfd, (struct sockaddr*) &servaddr, sizeof servaddr) < 0) {
	perror("bind");
}

/* Functions to convert between host and network byte order.

   Please note that these functions normally take `unsigned long int' or
   `unsigned short int' values as arguments and also return them.  But
   this was a short-sighted decision since on different systems the types
   may have different representations but the values are always the same.  */

extern uint32_t ntohl (uint32_t __netlong) __THROW __attribute__ ((__const__));
extern uint16_t ntohs (uint16_t __netshort)
     __THROW __attribute__ ((__const__));
extern uint32_t htonl (uint32_t __hostlong)
     __THROW __attribute__ ((__const__));
extern uint16_t htons (uint16_t __hostshort)
     __THROW __attribute__ ((__const__));

//成功时返回32位大端序整数型值，失败时返回INADDR_NONE，并且可以检测无效IP地址。
in_addr_t inet_addr(const char *__cp)

//成功时返回1（true），失败时返回0（false）
int inet_aton(const char *__cp, struct in_addr *__inp)

//成功时返回转换的字符串地址值，失败时返回-1
char *inet_ntoa(struct in_addr __in)

/* Convert from presentation format of an Internet number in buffer
   starting at CP to the binary network format and store result for
   interface type AF in buffer starting at BUF.  */
extern int inet_pton (int __af, const char *__restrict __cp,void *__restrict __buf) __THROW;

/* Convert a Internet address in binary network format for interface
   type AF in buffer starting at CP to presentation form and place
   result in buffer of length LEN astarting at BUF.  */
extern const char *inet_ntop (int __af, const void *__restrict __cp,char *__restrict __buf, socklen_t __len) __THROW;

#include <netinet/in.h>
#define INET_ADDRSTRLEN 16
#define INET6_ADDRSTRLEN 46

/* 自动获取服务端的计算机IP地址 */
#define	INADDR_ANY		((in_addr_t) 0x00000000)