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inet(3SOCKET)		   Sockets Library Functions		 inet(3SOCKET)

NAME
       inet,	inet6,	  inet_ntop,   inet_pton,   inet_addr,	 inet_network,
       inet_makeaddr, inet_lnaof, inet_netof, inet_ntoa	- Internet address ma-
       nipulation

SYNOPSIS
       cc [ flag ... ] file ...	-lsocket -lnsl [ library ... ]
       #include	<sys/types.h>
       #include	<sys/socket.h>
       #include	<netinet/in.h>
       #include	<arpa/inet.h>

       const char *inet_ntop(int af, const void	*addr, char *cp, size_t	size);

       int inet_pton(int af, const char	*cp, void *addr);

       in_addr_t inet_addr(const char *cp);

       in_addr_t inet_network(const char *cp);

       struct in_addr inet_makeaddr(const int net, const int lna);

       int inet_lnaof(const struct in_addr in);

       int inet_netof(const struct in_addr in);

       char *inet_ntoa(const struct in_addr in);

DESCRIPTION
       The  inet_ntop()	 and inet_pton() routines can manipulate both IPv4 and
       IPv6 addresses, whereas inet_addr(), inet_network(),   inet_makeaddr(),
       inet_lnaof(),  inet_netof(),  and  inet_ntoa() can only manipulate IPv4
       addresses.

       The inet_ntop() routine converts	a numeric address into a string	 suit-
       able for	presentation.  The af argument specifies the family of the ad-
       dress.  This can	be AF_INET or AF_INET6.	 The addr 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 cp argument points to a buffer	where the rou-
       tine will store the  resulting string.  The size	argument specifies the
       size  of	this buffer.  The application must specify a non-NULL cp argu-
       ment.  For IPv6 addresses, the buffer must be at	least 46-octets.   For
       IPv4 addresses, the buffer must be at least 16-octets.  In order	to al-
       low	applications to	easily declare buffers of the proper  size  to
       store  IPv4  and	 IPv6 addresses	in string form,	the following two con-
       stants  are defined in <netinet/in.h>:

       #define INET_ADDRSTRLEN	  16
       #define INET6_ADDRSTRLEN	  46

       The inet_pton() routine converts	an address in its standard text	  pre-
       sentation form into its numeric binary form.  The af argument specifies
       the family of the address.  Currently the AF_INET and  AF_INET6 address
       families	 are supported.	 The cp	argument points	to	the string be-
       ing passed in.  The addr	argument points	to a buffer  into   which  the
       routine	stores	the numeric address. The calling  application must en-
       sure that the buffer referred to	by addr	is	large enough  to  hold
       the  numeric  address,  at  least  4  bytes for AF_INET or 16 bytes for
       AF_INET6.

       The   inet_addr()  and  inet_network()  routines	 interpret   character
       strings	representing  numbers expressed	in the IPv4 standard `.' nota-
       tion, returning numbers suitable	for use	as  IPv4  addresses  and  IPv4
       network	numbers,  respectively.	 The  routine inet_makeaddr() takes an
       IPv4 network number and a local network address and constructs an  IPv4
       address from it.	The routines inet_netof() and inet_lnaof() break apart
       IPv4 host addresses, returning the network number and local network ad-
       dress part, respectively.

       The  inet_ntoa()	routine	 returns a pointer to a	string in the base 256
       notation	 d.d.d.d. See INTERNET ADDRESSES.

       Internet	addresses are returned in network order,  bytes	 ordered  from
       left  to	right. Network numbers and local address parts are returned as
       machine format integer values.

INTERNET ADDRESSES
   IPv6	Addresses
       There are three conventional forms for representing IPv6	addresses
	as strings:

       1. The preferred	form is	x:x:x:x:x:x:x:x, where the 'x's	are the	 hexa-
	  decimal  values of the eight 16-bit pieces of	the address, for exam-
	  ple,

	  1080:0:0:0:8:800:200C:417A

	  Note that it is not necessary	to write the leading zeros in an indi-
	  vidual  field.  However, there must be at least one numeral in every
	  field, except	as described below.

       2. Due to some methods of allocating certain styles of IPv6  addresses,
	  it  will  be	common	for  addresses to contain long strings of zero
	  bits.	 In order to make writing addresses containing zero  bits eas-
	  ier, a special syntax	is available to	compress the zeros. The	use of
	  "::" indicates multiple groups of 16-bits of	zeros.	The  "::"  can
	  only	appear once in an address.  The	"::" can also be  used to com-
	  press	the leading and/or trailing zeros in an	address. For example,

	  1080::8:800:200C:417A

       3. An alternative 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	 stan-
	  dard IPv4 representation address, for	example,

	  ::FFFF:129.144.52.38
	  ::129.144.52.38

	  where	 "::FFFF:d.d.d.d"  and "::d.d.d.d" are,	respectively, the gen-
	  eral forms of	an IPv4-mapped IPv6  address  and  an  IPv4-compatible
	  IPv6	address.  Note	that the IPv4 portion must be in the "d.d.d.d"
	  form.	The following forms are	invalid:

	  ::FFFF:d.d.d
	  ::FFFF:d.d
	  ::d.d.d
	  ::d.d

	  The following	form:

	  ::FFFF:d

	  is valid, however it is  an  unconventional  representation  of  the
	  IPv4-compatible IPv6 address,

	  ::255.255.0.d

	  while	   "::d"    corresponds	   to	the   general	IPv6   address
	  "0:0:0:0:0:0:0:d".

   IPv4	Addresses
       Values specified	using  `.' notation take one of	the following forms:

       d.d.d.d
       d.d.d
       d.d
       d

       When four parts are specified, each is interpreted as a	byte  of  data
       and assigned, from left to right, to the	four bytes of an IPv4 address.

       When a three part address is specified, the last	part is	interpreted as
       a 16-bit	quantity and placed in the right most two bytes	of the network
       address.	This makes the three part address format convenient for	speci-
       fying Class B network addresses as  128.net.host.

       When a two part address is supplied, the	last part is interpreted as  a
       24-bit quantity and placed in the right most three bytes	of the network
       address.	This makes the two part	address	format convenient for specify-
       ing Class A network addresses as	 net.host.

       When  only  one part is given, the value	is stored directly in the net-
       work address without any	byte rearrangement.

       With the	exception of inet_pton(), numbers supplied as  parts  in   `.'
       notation	 may  be decimal, octal, or hexadecimal, as specified in the C
       language. For example, a	leading	 0x or 0X implies hexadecimal;	other-
       wise,  a	leading	 0 implies octal; otherwise, the number	is interpreted
       as decimal.

       For IPv4	addresses, inet_pton() only accepts a string in	 the  standard
       IPv4 dotted-decimal form:

       d.d.d.d

       where  each number has one to three digits with a decimal value between
       0 and 255.

RETURN VALUES
       The inet_ntop() routine returns a pointer to the	 buffer	 containing  a
       string  if  the conversion succeeds, and	NULL otherwise.	 Upon failure,
       errno is	set to EAFNOSUPPORT if the af argument is invalid  or	ENOSPC
       if the size of the result buffer	is inadequate.

       inet_pton() returns 1 if	the conversion succeeds, 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.

       The  value  -1  is  returned by inet_addr() and inet_network() for mal-
       formed requests.

       The routines inet_netof() and inet_lnaof() break	apart  IPv4  host  ad-
       dresses,	 returning  the	network	number and local network address part,
       respectively.

       The routine inet_ntoa() returns a pointer to a string in	the  base  256
       notation	 d.d.d.d described in INTERNET ADDRESSES.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       gethostbyname(3NSL),  getipnodebyname(3SOCKET),	getnetbyname(3SOCKET),
       inet(3HEAD), hosts(4), ipnodes(4), networks(4), attributes(5)

NOTES
       The return value	from inet_ntoa() points	to a buffer which is overwrit-
       ten  on	each call.  This buffer	is implemented as thread-specific data
       in multithreaded	applications.

BUGS
       The problem of host byte	ordering versus	network	byte ordering is  con-
       fusing.	A  simple way to specify Class C network addresses in a	manner
       similar to that for Class B and Class A is needed.

SunOS 5.9			  3 Nov	1999			 inet(3SOCKET)

NAME | SYNOPSIS | DESCRIPTION | INTERNET ADDRESSES | RETURN VALUES | ATTRIBUTES | SEE ALSO | NOTES | BUGS

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