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<netdb.h>(0P)		   POSIX Programmer's Manual		 <netdb.h>(0P)

NAME
       netdb.h - definitions for network database operations

SYNOPSIS
       #include <netdb.h>

DESCRIPTION
       The  <netdb.h>  header  may define the in_port_t type and the in_addr_t
       type as described in <netinet/in.h> .

       The <netdb.h> header shall define the hostent structure	that  includes
       at least the following members:

	      char   *h_name	   Official name of the host.
	      char  **h_aliases	   A pointer to an array of pointers to
				   alternative host names, terminated by a
				   null pointer.
	      int     h_addrtype   Address type.
	      int     h_length	   The length, in bytes, of the address.
	      char  **h_addr_list  A pointer to an array of pointers to network
				   addresses (in network byte order) for the host,
				   terminated by a null pointer.

       The <netdb.h> header shall define the netent structure that includes at
       least the following members:

	      char     *n_name	    Official, fully-qualified (including the
				    domain) name of the host.
	      char    **n_aliases   A pointer to an array of pointers to
				    alternative network names, terminated by a
				    null pointer.
	      int	n_addrtype  The address type of the network.
	      uint32_t	n_net	    The network number, in host byte order.

       The uint32_t type shall be defined as described in <inttypes.h> .

       The <netdb.h> header shall define the protoent structure that  includes
       at least the following members:

	      char   *p_name	 Official name of the protocol.
	      char  **p_aliases	 A pointer to an array of pointers to
				 alternative protocol names, terminated by
				 a null pointer.
	      int     p_proto	 The protocol number.

       The  <netdb.h>  header shall define the servent structure that includes
       at least the following members:

	      char   *s_name	 Official name of the service.
	      char  **s_aliases	 A pointer to an array of pointers to
				 alternative service names, terminated by
				 a null pointer.
	      int     s_port	 The port number at which the service
				 resides, in network byte order.
	      char   *s_proto	 The name of the protocol to use when
				 contacting the service.

       The <netdb.h> header shall define the IPPORT_RESERVED  macro  with  the
       value of the highest reserved Internet port number.

       When  the <netdb.h> header is included, h_errno shall be available as a
       modifiable lvalue of type int. It is unspecified whether h_errno	 is  a
       macro or an identifier declared with external linkage.

       The <netdb.h> header shall define the following macros for use as error
       values for gethostbyaddr() and gethostbyname():

	      HOST_NOT_FOUND
	      NO_DATA
	      NO_RECOVERY
	      TRY_AGAIN

   Address Information Structure
       The <netdb.h> header shall define the addrinfo structure that  includes
       at least the following members:

	      int		ai_flags      Input flags.
	      int		ai_family     Address family of socket.
	      int		ai_socktype   Socket type.
	      int		ai_protocol   Protocol of socket.
	      socklen_t		ai_addrlen    Length of socket address.
	      struct sockaddr  *ai_addr	      Socket address of socket.
	      char	       *ai_canonname  Canonical name of service location.
	      struct addrinfo  *ai_next	      Pointer to next in list.

       The <netdb.h> header shall define the following macros that evaluate to
       bitwise-distinct integer constants for use in the flags	field  of  the
       addrinfo structure:

       AI_PASSIVE
	      Socket address is intended for bind().

       AI_CANONNAME

	      Request for canonical name.

       AI_NUMERICHOST

	      Return numeric host address as name.

       AI_NUMERICSERV

	      Inhibit service name resolution.

       AI_V4MAPPED
	      If  no  IPv6  addresses  are found, query for IPv4 addresses and
	      return them to the caller as IPv4-mapped IPv6 addresses.

       AI_ALL Query for both IPv4 and IPv6 addresses.

       AI_ADDRCONFIG

	      Query for IPv4 addresses only when an IPv4  address  is  config‐
	      ured; query for IPv6 addresses only when an IPv6 address is con‐
	      figured.

       The <netdb.h> header shall define the following macros that evaluate to
       bitwise-distinct	 integer  constants  for  use in the flags argument to
       getnameinfo():

       NI_NOFQDN
	      Only the nodename portion of the	FQDN  is  returned  for	 local
	      hosts.

       NI_NUMERICHOST

	      The  numeric  form  of the node's address is returned instead of
	      its name.

       NI_NAMEREQD
	      Return an error if the node's name  cannot  be  located  in  the
	      database.

       NI_NUMERICSERV

	      The  numeric  form of the service address is returned instead of
	      its name.

       NI_NUMERICSCOPE

	      For IPv6 addresses, the numeric form of the scope identifier  is
	      returned instead of its name.

       NI_DGRAM
	      Indicates that the service is a datagram service (SOCK_DGRAM).

   Address Information Errors
       The <netdb.h> header shall define the following macros for use as error
       values for getaddrinfo() and getnameinfo():

       EAI_AGAIN
	      The name could not be resolved at this time. Future attempts may
	      succeed.

       EAI_BADFLAGS
	      The flags had an invalid value.

       EAI_FAIL
	      A non-recoverable error occurred.

       EAI_FAMILY
	      The  address family was not recognized or the address length was
	      invalid for the specified family.

       EAI_MEMORY
	      There was a memory allocation failure.

       EAI_NONAME
	      The name does not resolve for the supplied parameters.

       NI_NAMEREQD is set and the host's name cannot be located, or both node‐
       name and servname were null.

       EAI_SERVICE
	      The  service  passed was not recognized for the specified socket
	      type.

       EAI_SOCKTYPE
	      The intended socket type was not recognized.

       EAI_SYSTEM
	      A system error occurred. The error code can be found in errno.

       EAI_OVERFLOW

	      An argument buffer overflowed.

       The following shall be declared as functions and may also be defined as
       macros. Function prototypes shall be provided.

	      void		endhostent(void);
	      void		endnetent(void);
	      void		endprotoent(void);
	      void		endservent(void);
	      void		freeaddrinfo(struct addrinfo *);
	      const char       *gai_strerror(int);
	      int		getaddrinfo(const char *restrict, const char *restrict,
				    const struct addrinfo *restrict,
				    struct addrinfo **restrict);
	      struct hostent   *gethostbyaddr(const void *, socklen_t, int);
	      struct hostent   *gethostbyname(const char *);
	      struct hostent   *gethostent(void);
	      int		getnameinfo(const struct sockaddr *restrict, socklen_t,
				    char *restrict, socklen_t, char *restrict,
				    socklen_t, int);
	      struct netent    *getnetbyaddr(uint32_t, int);
	      struct netent    *getnetbyname(const char *);
	      struct netent    *getnetent(void);
	      struct protoent  *getprotobyname(const char *);
	      struct protoent  *getprotobynumber(int);
	      struct protoent  *getprotoent(void);
	      struct servent   *getservbyname(const char *, const char *);
	      struct servent   *getservbyport(int, const char *);
	      struct servent   *getservent(void);
	      void		sethostent(int);
	      void		setnetent(int);
	      void		setprotoent(int);
	      void		setservent(int);

       The  type  socklen_t  shall  be defined through typedef as described in
       <sys/socket.h>.

       Inclusion of the <netdb.h> header may also  make	 visible  all  symbols
       from <netinet/in.h>, <sys/socket.h>, and <inttypes.h>.

       The following sections are informative.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <netinet/in.h>,	<inttypes.h>,  <sys/socket.h>,	the  System Interfaces
       volume of IEEE Std 1003.1-2001, bind(), endhostent(), endnetent(), end‐
       protoent(), endservent(), getaddrinfo(), getnameinfo()

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, Copyright (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.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			 <netdb.h>(0P)
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