socket学习笔记——获取域名与IP(linux)

gethostbyname.c

 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <arpa/inet.h>
 #include <netdb.h>

 int main(int argc,char* argv[])
 {
     int i;
     struct hostent* host;
     if(argc != )
     {
         printf("usage: %s <addr>\n",argv[]);
         exit();
     }

     host = gethostbyname(argv[]);
     if(!host)
     {
         printf("get host error......\n");
         exit();
     }
     printf("official name:%s\n",host->h_name);
     for(i = ;host->h_aliases[i];i++)
         printf("access %d; %s\n",i+,host->h_aliases[i]);
     printf("address type:%s \n",(host->h_addrtype==AF_INET)?"AF_INET":"AFINET6");
     for(i = ;host->h_addr_list[i];i++)
         printf("IP addr %d: %s \n",i+,inet_ntoa(*(struct in_addr*)host->h_addr_list[i]));
     return ;
 }

gethostbyaddr.c

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <netdb.h>

 int main(int argc,char* argv[])
 {
     int i;
     struct hostent* host;
     struct sockaddr_in addr;
     if(argc != )
     {
         printf("usage :%s <ip>\n",argv[]);
         exit();
     }

     memset(&addr,,sizeof(addr));
     addr.sin_addr.s_addr = inet_addr(argv[]);
     host = gethostbyaddr((char*)&addr.sin_addr,,AF_INET);
     if(!host)
     {
         printf("get host error\n");
         exit();
     }

     printf("official name;%s \n",host->h_name);
     for(i = ;host->h_aliases[i];i++)
         printf("aliases %d:%s\n",i,host->h_aliases[i]);
     printf("address type:%s\n",(host->h_addrtype==AF_INET)?"AF_INET":"AF_INET6");
     for(i = ;host->h_addr_list[i];i++)
         printf("IP addr %d;%s\n",i+,inet_ntoa(*(struct in_addr*)host->h_addr_list[i]));
     return ;
 }