netdb(3HEAD)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO

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(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	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 network.
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(3HEAD).

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 can 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 can 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);

SEE ALSO

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

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO