/*
 * whoisserver.c - main
 * from Doug Comer Internetworking with TCP/IP vol 1 pp. 359
 */
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <pwd.h>

#define bcopy(a,b,c) strncpy(b,a,c)    /* for those who don't have bcopy */
/*----------------------------------------------------------
 * Program      : whoisserver
 * Purpose      : UNIX application program that acts as a server
 *                for 'whois' service on the local machine. It listens
 *                on well-known WHOIS port (43) and answers queries from
 *                clients. This program requires super-user privilege to
 *                run.
 * Use          : whois hostname username
 * Author       : Barry Shein, Boston University
 * Date         : January, 1987
 *
 * Modification : Since the original program requires super-user privilege
 *                we modify the program to use a non-privilege port so
 *                every one can execute it. We use the port 2500 (randomly
 *                chosen.
 *                Xiannong Meng, Bucknell University, 1/16/93
 *----------------------------------------------------------
 */

#define BACKLOG          5          /* # of requests to queue              */
#define MAXHOSTNAME      32         /* maximum host name length            */

#define WHOISPORT        2500       /* a non-privilege port so all can use */

main(argc,argv)
int argc;
char *argv[];
{
   int s, t;                        /* socket descriptor                   */
   int i;                           /* general purpose integer             */
   struct sockaddr_in sa, isa;      /* internet socket structure           */
   struct hostent *hp;              /* host name structure                 */
   char *myname;                    /* pointer to the name of this program */
   struct servent *sp;              /* pointer to srevice entry            */
   char localhost[MAXHOSTNAME+1];   /* local host name as character string */

   myname = argv[0];
   /*
    * Get our own host information
    */
   gethostname(localhost,MAXHOSTNAME);
   if ((hp = gethostbyname(localhost)) == NULL)
   {
      fprintf(stderr,"%s: Cannnot get local host info.\n",myname);
      exit(1);
   }
   
   /*
    * Put the WHOIS socket number and our address info
    * into the socket structure
    */
   sa.sin_port = WHOISPORT;
   bcopy((char *)hp->h_addr,(char *)&sa.sin_addr,hp->h_length);
   sa.sin_family = hp->h_addrtype;

   /*
    * The following line is added by X. Meng
    * without it, bind() fails.
    */
   sa.sin_addr.s_addr = htonl(INADDR_ANY);

   /*
    * Allocate an open socket for the incoming connections
    */
   if ((s = socket(hp->h_addrtype,SOCK_STREAM,0)) < 0)
   {
      perror("socket");
      exit(1);
   }
   /*
    * Bind the socket to the service port so
    * we can hear incoming connection
    */
    if (bind(s,(struct sockaddr *)(&sa),sizeof sa) < 0)
    {
       perror("bind");
       exit(1);
    }
    /*
     * Set maximum connections we will fall behind
     */
    listen(s, BACKLOG);

    /*
     * Go into an infinite loop waiting for new connections
     */
   while (1)
   {
      i = sizeof sa;
      /*
       * We hang in accept() while waiting for new customers
       */
      if ((t = accept(s,(struct sockaddr *)(&isa),&i)) < 0)
      {
         perror("accept");
         exit(1);
      }
      whois(t);      /* perform the actual WHOIS service */
      close(t);
   }
}

/*
 * Get the WHOIS request from remote host and format a reply
 */
whois(sock)
int sock;
{
   struct passwd *p;
   char buf[BUFSIZ+1];
   int i;

   /*
    * Get one line request
    */
   if ((i = read(sock,buf,BUFSIZ)) <= 0)
      return;
   buf[i] = '\0';
   /*
    * Look up the requested user and format a reply
    */
   if ((p = getpwnam(buf)) == NULL)
       strcpy(buf,"User not found\n");
   else
   /*
    * 'pw_name' is the user login name
    * 'pw_gecos' is the real name section
    */
       sprintf(buf,"%s: %s\n",p->pw_name,p->pw_gecos);
   /*
    * Return reply
    */
   write(sock,buf,strlen(buf));
   return;
}