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

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 follow-
       ing 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 follow-
       ing 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  fol-
       lowing 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 follow-
       ing 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 geth-
       ostbyaddr() 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  fol-
       lowing 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 configured; query for IPv6
	      addresses only when an IPv6 address is configured.

       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  getad-
       drinfo() 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  nodename  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(),  endprotoent(),  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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

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