main() 
     { 
          ... 
          sp = getservbyname("who", "udp"); 
          net = getnetbyname("localnet"); 
          sin.sin_addr = inet_makeaddr(INADDR_ANY, net); 
          sin.sin_port = sp->s_port; 
          ... 
          s = socket(AF_INET, SOCK_DGRAM, 0); 
          ... 
          on = 1; 
          if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on)) < 0) { 
               syslog(LOG_ERR, "setsockopt SO_BROADCAST: %m"); 
               exit(1); 
          } 
          bind(s, (struct sockaddr *) &sin, sizeof (sin)); 
          ... 
          signal(SIGALRM, onalrm); 
          onalrm(); 
          for (;;) { 
               struct whod wd; 
               int cc, whod, len = sizeof (from);

               cc = recvfrom(s, (char *)&wd, sizeof (struct whod), 0, 
                    (struct sockaddr *)&from, &len); 
               if (cc <= 0) { 
                    if (cc < 0 && errno != EINTR) 
                         syslog(LOG_ERR, "rwhod: recv: %m"); 
                    continue; 
               } 
               if (from.sin_port != sp->s_port) { 
                    syslog(LOG_ERR, "rwhod: %d: bad from port", 
                         ntohs(from.sin_port)); 
                    continue; 
               } 
               ... 
               if (!verify(wd.wd_hostname)) { 
                    syslog(LOG_ERR, "rwhod: malformed host name from %x", 
                         ntohl(from.sin_addr.s_addr)); 
                    continue; 
               } 
               (void) sprintf(path, "%s/whod.%s", RWHODIR, wd.wd_hostname); 
               whod = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0666); 
               ... 
               (void) time(&wd.wd_recvtime); 
               (void) write(whod, (char *)&wd, cc); 
               (void) close(whod); 
          } 
     }