These additional functions for manipulating Internet addresses are declared in the header file arpa/inet.h. They represent Internet addresses in network byte order, and network numbers and local-address-within-network numbers in host byte order. See Byte Order Conversion, for an explanation of network and host byte order.
int
inet_aton (const char *name, struct in_addr *addr)
¶Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function converts the IPv4 Internet host address name
from the standard numbers-and-dots notation into binary data and stores
it in the struct in_addr
that addr points to.
inet_aton
returns nonzero if the address is valid, zero if not.
uint32_t
inet_addr (const char *name)
¶Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function converts the IPv4 Internet host address name from the
standard numbers-and-dots notation into binary data. If the input is
not valid, inet_addr
returns INADDR_NONE
. This is an
obsolete interface to inet_aton
, described immediately above. It
is obsolete because INADDR_NONE
is a valid address
(255.255.255.255), and inet_aton
provides a cleaner way to
indicate error return.
uint32_t
inet_network (const char *name)
¶Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function extracts the network number from the address name,
given in the standard numbers-and-dots notation. The returned address is
in host order. If the input is not valid, inet_network
returns
-1
.
The function works only with traditional IPv4 class A, B and C network types. It doesn’t work with classless addresses and shouldn’t be used anymore.
char *
inet_ntoa (struct in_addr addr)
¶Preliminary: | MT-Safe locale | AS-Unsafe race | AC-Safe | See POSIX Safety Concepts.
This function converts the IPv4 Internet host address addr to a string in the standard numbers-and-dots notation. The return value is a pointer into a statically-allocated buffer. Subsequent calls will overwrite the same buffer, so you should copy the string if you need to save it.
In multi-threaded programs each thread has its own statically-allocated
buffer. But still subsequent calls of inet_ntoa
in the same
thread will overwrite the result of the last call.
Instead of inet_ntoa
the newer function inet_ntop
which is
described below should be used since it handles both IPv4 and IPv6
addresses.
struct in_addr
inet_makeaddr (uint32_t net, uint32_t local)
¶Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function makes an IPv4 Internet host address by combining the network number net with the local-address-within-network number local.
uint32_t
inet_lnaof (struct in_addr addr)
¶Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function returns the local-address-within-network part of the Internet host address addr.
The function works only with traditional IPv4 class A, B and C network types. It doesn’t work with classless addresses and shouldn’t be used anymore.
uint32_t
inet_netof (struct in_addr addr)
¶Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function returns the network number part of the Internet host address addr.
The function works only with traditional IPv4 class A, B and C network types. It doesn’t work with classless addresses and shouldn’t be used anymore.
int
inet_pton (int af, const char *cp, void *buf)
¶Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function converts an Internet address (either IPv4 or IPv6) from
presentation (textual) to network (binary) format. af should be
either AF_INET
or AF_INET6
, as appropriate for the type of
address being converted. cp is a pointer to the input string, and
buf is a pointer to a buffer for the result. It is the caller’s
responsibility to make sure the buffer is large enough.
const char *
inet_ntop (int af, const void *cp, char *buf, socklen_t len)
¶Preliminary: | MT-Safe locale | AS-Safe | AC-Safe | See POSIX Safety Concepts.
This function converts an Internet address (either IPv4 or IPv6) from
network (binary) to presentation (textual) form. af should be
either AF_INET
or AF_INET6
, as appropriate. cp is a
pointer to the address to be converted. buf should be a pointer
to a buffer to hold the result, and len is the length of this
buffer. The return value from the function will be this buffer address.