socket学习笔记——获取域名与IP(linux)

gethostbyname.c

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <unistd.h>
 4 #include <arpa/inet.h>
 5 #include <arpa/inet.h>
 6 #include <netdb.h>
 7
 8 int main(int argc,char* argv[])
 9 {
10     int i;
11     struct hostent* host;
12     if(argc != 2)
13     {
14         printf("usage: %s <addr>\n",argv[0]);
15         exit(1);
16     }
17
18     host = gethostbyname(argv[1]);
19     if(!host)
20     {
21         printf("get host error......\n");
22         exit(1);
23     }
24     printf("official name:%s\n",host->h_name);
25     for(i = 0;host->h_aliases[i];i++)
26         printf("access %d; %s\n",i+1,host->h_aliases[i]);
27     printf("address type:%s \n",(host->h_addrtype==AF_INET)?"AF_INET":"AFINET6");
28     for(i = 0;host->h_addr_list[i];i++)
29         printf("IP addr %d: %s \n",i+1,inet_ntoa(*(struct in_addr*)host->h_addr_list[i]));
30     return 0;
31 }

gethostbyaddr.c

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <string.h>
 4 #include <unistd.h>
 5 #include <arpa/inet.h>
 6 #include <netdb.h>
 7
 8 int main(int argc,char* argv[])
 9 {
10     int i;
11     struct hostent* host;
12     struct sockaddr_in addr;
13     if(argc != 2)
14     {
15         printf("usage :%s <ip>\n",argv[0]);
16         exit(1);
17     }
18
19     memset(&addr,0,sizeof(addr));
20     addr.sin_addr.s_addr = inet_addr(argv[1]);
21     host = gethostbyaddr((char*)&addr.sin_addr,4,AF_INET);
22     if(!host)
23     {
24         printf("get host error\n");
25         exit(1);
26     }
27
28     printf("official name;%s \n",host->h_name);
29     for(i = 0;host->h_aliases[i];i++)
30         printf("aliases %d:%s\n",i,host->h_aliases[i]);
31     printf("address type:%s\n",(host->h_addrtype==AF_INET)?"AF_INET":"AF_INET6");
32     for(i = 0;host->h_addr_list[i];i++)
33         printf("IP addr %d;%s\n",i+1,inet_ntoa(*(struct in_addr*)host->h_addr_list[i]));
34     return 0;
35 }