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NETDB.H 3HEAD "Sep 10, 2004"
NAME
netdb.h, netdb - definitions for network database operations
SYNOPSIS

#include <netdb.h>
DESCRIPTION

The <netdb.h> header defines the type in_port_t and the type in_addr_t as described in in.h(3HEAD).

The <netdb.h> header defines the hostent structure that includes the following members:

char *h_name /* official name of the host */
char **h_aliases /* pointer to an array of pointers to
 alternative host names, terminated
 by a null pointer */
int h_addrtype /* address type */
int h_length /* length, in bytes, of the address */
char **h_addr_list /* 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 defines the netent structure that includes the following members:

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

The <netdb.h> header defines the protoent structure that includes the following members:

char *p_name /* official name of the protocol */
char **p_aliases /* pointer to an array of pointers to
 alternative protocol names, terminated
 by a null pointer */
int p_proto /* protocol number */

The <netdb.h> header defines the servent structure that includes the following members:

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

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

The <netdb.h> header provides a declaration for h_errno:

extern int h_errno;

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

HOST_NOT_FOUND NO_DATA
NO_RECOVERY TRY_AGAIN

Inclusion of the <netdb.h> header may also make visible all symbols from in.h(3HEAD).

ATTRIBUTES

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

ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Standard
SEE ALSO

Intro(3), endhostent(3NSL), endhostent(3XNET), endnetent(3SOCKET), endnetent(3XNET), endprotoent(3SOCKET), endprotoent(3XNET), endservent(3SOCKET), endservent(3XNET), in.h(3HEAD), attributes(5), standards(5)