Originální popis anglicky:
netdb.h - definitions for network database operations
Návod, kniha: POSIX Programmer's Manual
#include <netdb.h>
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
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 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).
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
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.
None.
None.
None.
<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()
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
.
