Functions related to socket address parsing: inet_addr, inet_ntoa, gethostname, gethostbyname

# Include <sys/socket. h>
# Include <netdb. h> // hostent, gethostbyname gethostbyaddr
# Include <string. h> // memcpy
# Include <netinet/in. h>
# Include <ARPA/inet. h> // inet_ntop
# Include <unistd. h>
# Include <stdlib. h>
# Include <stdio. h>
Int main (void)
{
Unsigned long d;
Struct in_addr ADDR;
Char * IP = "192.168.1.11 ";
D = inet_addr (IP );
Memcpy (& ADDR, & D, 4); // although inet_addr and inet_ntoa are reciprocal functions, the values obtained using inet_addr cannot be directly used in inet_ntoa, you need to use this method to convert to the in_addr type.
Printf ("long format: % lu \ n", d );
Printf ("convert to STR: % s \ n", inet_ntoa (ADDR ));
Char host [32] = {0 };
Gethostname (host, sizeof (host ));
Printf ("host name is: % s \ n", host );
Char * BD = "www.baidu.com ";
Struct hostent * HbD;
// Gethostbyname: obtains the IP address through the domain name. This function returns a hostent structure pointer, which can be used only after further conversion.
HbD = gethostbyname (BD );
// The command h_addr_list contains garbled characters, which cannot be directly typed. You need to use the inet_ntop
Printf ("after gethostbyname: % s, % s, % d, % d, % s \ n", hBD-> h_name, * HbD-> h_aliases, hBD-> h_addrtype, hbD-> h_length, * HbD-> h_addr_list );
Char ipbd [32] = {0 };
Inet_ntop (HbD-> h_addrtype, * HbD-> h_addr_list, ipbd, sizeof (ipbd ));
Printf ("real IP is: % s \ n", ipbd );
Return 0;
}