Mapping host names (Internet domain)
An Internet host name to address mapping is represented by the
hostent data structure:
struct hostent {
char *h_name;
char **h_aliases;
int h_addrtype;
int h_length;
char **h_addr_list;
# define h_addr h_addr_list[0]
}
*h_name-
is the official name of the host.
**h_aliases-
is the alias list.
h_addrtype-
is the host address type.
h_length-
is the length of address.
h_addr_list-
is the address list.
h_addr-
is the primary address.
The routine gethostbyname takes an Internet host name and
returns a hostent structure.
The gethostbyaddr routine maps Internet
host addresses into a hostent structure.
These two routines search for the contents for this structure
in any or all of the following databases:
the Domain Name Service (DNS),
the Network Information Service (NIS),
and the file /etc/hosts.
The order and number of databases searched depends on the value
assigned to the keyword hostresorder in the file
/etc/resolv.conf (see
resolver(SFF)).
Note: These routines do not read /etc/resolv.conf directly.
They invoke the resolver routine res_init (see
resolver(SLIB)).
If a host has more than one address associated with the same name,
gethostbyname returns only the first entry found unless searching
the DNS database; DNS returns all addresses
associated with a host name.
(inet_netof is a standard routine which returns the
network portion of an Internet address. See
inet(SLIB).
Next topic:
Mapping network names (Internet domain)
Previous topic:
Networking library routines used for Internet sockets
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003