INET_NTOP(3P)                                       POSIX Programmer's Manual                                      INET_NTOP(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       inet_ntop, inet_pton - convert IPv4 and IPv6 addresses between binary and text form

SYNOPSIS
       #include <arpa/inet.h>

       const char *inet_ntop(int af, const void *restrict src,
              char *restrict dst, socklen_t size);
       int inet_pton(int af, const char *restrict src, void *restrict dst);


DESCRIPTION
       The  inet_ntop()  function  shall convert a numeric address into a text string suitable for presentation. The af argument
       shall specify the family of the address. This can be AF_INET  or AF_INET6.  The src argument points to a  buffer  holding
       an  IPv4  address if the af argument is AF_INET,  or an IPv6 address if the af argument is AF_INET6;  the address must be
       in network byte order. The dst argument points to a buffer where the function stores the resulting text string; it  shall
       not  be  NULL.  The  size argument specifies the size of this buffer, which shall be large enough to hold the text string
       (INET_ADDRSTRLEN characters for IPv4,  INET6_ADDRSTRLEN characters for IPv6).

       The inet_pton() function shall convert an address in its standard text presentation form into its  numeric  binary  form.
       The  af  argument shall specify the family of the address. The AF_INET  and AF_INET6 address families shall be supported.
       The src argument points to the string being passed in. The dst argument points to a buffer into which the function stores
       the  numeric  address;  this  shall  be  large  enough  to  hold  the numeric address (32 bits for AF_INET,  128 bits for
       AF_INET6).

       If the af argument of inet_pton() is AF_INET, the src string shall be in the standard IPv4 dotted-decimal form:


              ddd.ddd.ddd.ddd

       where "ddd" is a one to three digit decimal number between 0 and 255 (see inet_addr()). The inet_pton() function does not
       accept  other  formats  (such  as  the  octal  numbers, hexadecimal numbers, and fewer than four numbers that inet_addr()
       accepts).

       If the af argument of inet_pton() is AF_INET6, the src string shall be in one of the following standard IPv6 text forms:

        1. The preferred form is "x:x:x:x:x:x:x:x", where the 'x' s are the hexadecimal values of the eight 16-bit pieces of the
           address. Leading zeros in individual fields can be omitted, but there shall be at least one numeral in every field.

        2. A  string  of contiguous zero fields in the preferred form can be shown as "::" . The "::" can only appear once in an
           address. Unspecified addresses ( "0:0:0:0:0:0:0:0" ) may be represented simply as "::" .

        3. A third form that is sometimes more convenient when dealing with a mixed  environment  of  IPv4  and  IPv6  nodes  is
           "x:x:x:x:x:x:d.d.d.d", where the 'x' s are the hexadecimal values of the six high-order 16-bit pieces of the address,
           and the 'd' s are the decimal values of the four low-order 8-bit pieces of the  address  (standard  IPv4  representa-
           tion).

       Note:  A more extensive description of the standard representations of IPv6 addresses can be found in RFC 2373.


RETURN VALUE
       The  inet_ntop() function shall return a pointer to the buffer containing the text string if the conversion succeeds, and
       NULL otherwise, and set errno to indicate the error.

       The inet_pton() function shall return 1 if the conversion succeeds, with the address pointed to by dst  in  network  byte
       order.  It  shall return 0 if the input is not a valid IPv4 dotted-decimal string  or a valid IPv6 address string,  or -1
       with errno set to [EAFNOSUPPORT] if the af argument is unknown.

ERRORS
       The inet_ntop() and inet_pton() functions shall fail if:

       EAFNOSUPPORT

              The af argument is invalid.

       ENOSPC The size of the inet_ntop() result buffer is inadequate.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       The Base Definitions volume of IEEE Std 1003.1-2001, <arpa/inet.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                 INET_NTOP(3P)