#include <netdb.h>

struct hostent *gethostbyname(const char *name);
			

struct hostent
{
    char *h_name;         /* 호스트의 공식 이름 */
    char **h_aliases;     /* 별칭 리스트 */
    int  h_addrtype;      /* 호스트 주소 타입 */
    int  h_length;        /* 주소의 길이 */ 
    char **h_addr_list;   /* 주소 리스트 */
}
			

search localhost
nameserver 211.62.36.242
nameserver 164.124.101.2
			

#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

int main(int argc, char **argv)
{
    struct hostent     *myent;
    struct in_addr    myen;
    long int *add;

    myent = gethostbyname(argv[1]);
    if (myent == NULL)
    {
        perror("ERROR : ");
        exit(0);
    }

    printf("%s\n", myent->h_name);

    while(*myent->h_addr_list != NULL)
    {
        add = (long int *)*myent->h_addr_list;
        myen.s_addr = *add;
        printf("%s\n", inet_ntoa(myen));
        myent->h_addr_list++;
    }
}
			

[root@localhost test]# ./gethostbyname www.joinc.co.kr
www.joinc.co.kr
211.234.96.147
[root@localhost test]# ./gethostbyname www.yahoo.com  
www.yahoo.akadns.net
66.218.71.83
66.218.71.84
66.218.71.86
66.218.71.87
66.218.71.89
66.218.71.80
66.218.71.81
			

                            +---------------------------------------+
                            | Server                                | 
 +---------+                | +-+     +--------+         +--------+ |
 | client1 | <------------> | |P|<--->| accept |<------->| 처리 1 | |
 +---------+                | |O|     |        |    |    +--------+ |
 +---------+                | |R|     |        |    |    +--------+ |
 | client2 | <------------> | |T|     |        |    +--->| 처리 2 | |
 +---------+                | +-+     +--------+         +--------+ |
                            +---------------------------------------+

 -->> : fork & exec
 +---------+            +-------+         +----------+
 | client1 | ---------> | inetd | ----->> | Server 1 |
 +---------+            |       |         +----------+
 +---------+            |       |         +----------+
 | client1 | ---------> |       | ----->> | Server 2 |
 +---------+            +-------+         +----------+

#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>

int main(int argc, char **argv)
{
    struct sockaddr *clientaddr; 
    char buf[255];
    char line[255];
    char myline[255];
    FILE *fp;
    int  length;

    clientaddr = (struct sockaddr *)malloc(128);
    length = 128;

    if (getpeername(0, clientaddr, &length) < 0)
    {
        perror("socket failure: ");
        exit(0);
    }

    if ((fp=fopen("/etc/zipcode.txt", "r")) == NULL)
    {
        perror("file open error : ");
        exit(0);
    }
    while(1)
    {
        if (read(0, buf, 255) <= 0)
            break;
        if (strncmp(buf, "quit", 4) == 0)
        {
            write(0, "byebye\n", 8); 
            break;
        }

        while(fgets(line,255,fp) != NULL)
        {
            if (strstr(line, buf) != NULL)
            {
                write(0, line, 255);
            }
        }
        write(0, "end\n", 4);
        rewind(fp);
    }

    close(0);
    fclose(fp);
    exit(0);
}