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 != 2)
    {
        printf("usage: %s <addr>
",argv[0]);
        exit(1);
    }

    host = gethostbyname(argv[1]);
    if(!host)
    {
        printf("get host error......
");
        exit(1);
    }
    printf("official name:%s
",host->h_name);
    for(i = 0;host->h_aliases[i];i++)
        printf("access %d; %s
",i+1,host->h_aliases[i]);
    printf("address type:%s 
",(host->h_addrtype==AF_INET)?"AF_INET":"AFINET6");
    for(i = 0;host->h_addr_list[i];i++)
        printf("IP addr %d: %s 
",i+1,inet_ntoa(*(struct in_addr*)host->h_addr_list[i]));
    return 0;
}

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 != 2)
    {
        printf("usage :%s <ip>
",argv[0]);
        exit(1);
    }

    memset(&addr,0,sizeof(addr));
    addr.sin_addr.s_addr = inet_addr(argv[1]);
    host = gethostbyaddr((char*)&addr.sin_addr,4,AF_INET);
    if(!host)
    {
        printf("get host error
");
        exit(1);
    }

    printf("official name;%s 
",host->h_name);
    for(i = 0;host->h_aliases[i];i++)
        printf("aliases %d:%s
",i,host->h_aliases[i]);
    printf("address type:%s
",(host->h_addrtype==AF_INET)?"AF_INET":"AF_INET6");
    for(i = 0;host->h_addr_list[i];i++)
        printf("IP addr %d;%s
",i+1,inet_ntoa(*(struct in_addr*)host->h_addr_list[i]));
    return 0;
}