netdb(5)

NAME

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(5).

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

char	∗h_name	Official name of the net.
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 defines the netent structure that includes 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.
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	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 defines the servent structure that includes 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 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(5).

Default

For applications that do not require standard-conforming behavior (those that use the socket interfaces described in section 3N of the reference manual; see Intro(3) and standards(5)), the following are declared as functions, and may also be defined as macros:

int	endhostent(void);
int	endnetent(void);
int	endprotoent(void);
int	endservent(void);
struct hostent	∗gethostbyaddr(const void ∗addr, int len, int type);
struct hostent	∗gethostbyname(const char ∗name);
struct hostent	∗gethostent(void);
struct netent	∗getnetbyaddr(long net, int type);
struct netent	∗getnetbyname(const char ∗name);
struct netent	∗getnetent(void);
struct protoent	∗getprotobyname(const char ∗name);
struct protoent	∗getprotobynumber(int proto);
struct protoent	∗getprotoent(void);
struct servent	∗getservbyname(const char ∗name, const char ∗proto);
struct servent	∗getservbyport(int port, const char ∗proto);
struct servent	∗getservent(void);
int	sethostent(int stayopen);
int	setnetent(int stayopen);
int	setprotoent(int stayopen);
int	setservent(int stayopen);

Standard-conforming

For applications that require standard-conforming behavior (those that use the socket interfaces described in section 3XN of the reference manual; see Intro(3) and standards(5)), the following are declared as functions, and may also be defined as macros:

void	endhostent(void);
void	endnetent(void);
void	endprotoent(void);
void	endservent(void);
struct hostent	∗gethostbyaddr(const void ∗addr, size_t len, int type);
struct hostent	∗gethostbyname(const char ∗name);
struct hostent	∗gethostent(void);
struct netent	∗getnetbyaddr(in_addr_t net, int type);
struct netent	∗getnetbyname(const char ∗name);
struct netent	∗getnetent(void);
struct protoent	∗getprotobyname(const char ∗name);
struct protoent	∗getprotobynumber(int proto);
struct protoent	∗getprotoent(void);
struct servent	∗getservbyname(const char ∗name, const char ∗proto);
struct servent	∗getservbyport(int port, const char ∗proto);
struct servent	∗getservent(void);
void	sethostent(int stayopen);
void	setnetent(int stayopen);
void	setprotoent(int stayopen);
void	setservent(int stayopen);

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