/*
 * NAME:        TCPServer SYNOPSIS:    TCPServer [port]
 * 
 * DESCRIPTION:  The program creates a TCP socket in the inet listen for
 * connections from TCPClients, accept clients into private sockets, and use
 * select to  echo ``serve'' the client. If [port] is not specified, the
 * program uses any available port.
 * 
 */

#include "def"

#define MAXHOSTNAME 80
#define MAXCLIENTS  10
void            reusePort(int sock);

int             client[MAXCLIENTS];
fd_set          readset, allset;
int             i;

main(argc, argv)
   int             argc;
   char           *argv[];
{
   int             sd, psd;
   struct sockaddr_in server;
   struct hostent *hp, *gethostbyname();
   struct servent *sp;
   struct sockaddr_in from[MAXCLIENTS];
   struct sockaddr_in fromi;
   int             fromlen;
   int             length;
   char            ThisHost[80];
   int             pn;
   int             childpid;
   int nb;
   struct timeval wait;
   int TIMEOUT = 0;




   sp = getservbyname("echo", "tcp");
   /* get TCPServer1 Host information, NAME and INET ADDRESS */

   gethostname(ThisHost, MAXHOSTNAME);
   /* OR strcpy(ThisHost,"localhost"); */

   printf("----TCP/Server running at host NAME: %s\n", ThisHost);
   if ((hp = gethostbyname(ThisHost)) == NULL) {
      fprintf(stderr, "Can't find host %s\n", argv[1]);
      exit(-1);
   }
   bcopy(hp->h_addr, &(server.sin_addr), hp->h_length);
   printf("    (TCP/Server INET ADDRESS is: %s )\n", inet_ntoa(server.sin_addr));


   /** Construct name of socket */
   server.sin_family = AF_INET;
   /* OR server.sin_family = hp->h_addrtype; */

   server.sin_addr.s_addr = htonl(INADDR_ANY);
   if (argc == 1)
      server.sin_port = htons(0);
   else {
      pn = htons(atoi(argv[1]));
      server.sin_port = pn;
   }
   /* OR    server.sin_port = sp->s_port; */

   /** Create socket on which to send  and receive */

   sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
   /* OR sd = socket (hp->h_addrtype,SOCK_STREAM,0); */
   if (sd < 0) {
      perror("opening stream socket");
      exit(-1);
   }
   /** this allow the server to re-start quickly instead of fully wait
                 for TIME_WAIT which can be as large as 2 minutes */
   reusePort(sd);
   if (bind(sd, (SA *) & server, sizeof(server)) < 0) {
      close(sd);
      perror("binding name to stream socket");
      exit(-1);
   }
   /** get port information and  prints it out */
   length = sizeof(server);
   if (getsockname(sd, (SA *) & server, &length)) {
      perror("getting socket name");
      exit(0);
   }
   printf("Server Port is: %d\n", ntohs(server.sin_port));

   /** accept TCP connections from clients and use select to serve each */
   listen(sd, 4);
   fromlen = sizeof(fromi);
   for (i = 0; i < MAXCLIENTS; i++)
      client[i] = -1;   /* -1 indicates available entry */
   FD_ZERO(&allset);
   FD_SET(sd, &allset);

   wait.tv_sec = 1;
   wait.tv_usec = 0;


   for (;;) {
      readset = allset;   /* structure assignment */
      
      if (TIMEOUT)
          nb = select(MAXCLIENTS, &readset, NULL, NULL, NULL);
      else
          nb = select(MAXCLIENTS, &readset, NULL, NULL, &wait);

      if (nb == 0){
               printf("TIME OUT\n");
               TIMEOUT = 1;
      }
      if (FD_ISSET(sd, &readset)) {   /* new client connection */

         psd = accept(sd, (SA *) & fromi, &fromlen);
         for (i = 0; i < MAXCLIENTS; i++)
            if (client[i] < 0) {
               client[i] = psd;   /* save descriptor */
               from[i]=fromi;
               FD_SET(psd, &allset);   /* add new descriptor to set */
               break;
            }
         if (i == MAXCLIENTS) {
            printf("too many clients");
            exit(0);
         }
      }
      for (i = 0; i <= MAXCLIENTS; i++) {   /* check all clients for
                      * data */
         if ((psd = client[i]) < 0)
            continue;
         if (FD_ISSET(psd, &readset))
            EchoServe(psd, from[i], i);
      }
   }
}

EchoServe(psd, from, i)
   int             psd;
   struct sockaddr_in from;
   int             i;
{
   char            buf[512];
   int             rc;
   struct hostent *hp, *gethostbyname();

   printf("Serving %s:%d\n", inet_ntoa(from.sin_addr),
          ntohs(from.sin_port));
   if ((hp = gethostbyaddr((char *) &from.sin_addr.s_addr,
             sizeof(from.sin_addr.s_addr), AF_INET)) == NULL)
      fprintf(stderr, "Can't find host %s\n", inet_ntoa(from.sin_addr));
   else
      printf("(Name is : %s)\n", hp->h_name);

   /**  get data from  clients and send it back */
   printf("\n...server is waiting...\n");
   if ((rc = recv(psd, buf, sizeof(buf), 0)) < 0) {
      perror("receiving stream  message");
   }
   if (rc > 0) {
      buf[rc] = NULL;
      printf("Received: %s\n", buf);
      printf("From TCP/Client: %s:%d\n", inet_ntoa(from.sin_addr),
             ntohs(from.sin_port));
      printf("(Name is : %s)\n", hp->h_name);
      if (send(psd, buf, rc, 0) < 0)
         perror("sending stream message");
   } else {
      printf("TCP/Client: %s:%d\n", inet_ntoa(from.sin_addr),
             ntohs(from.sin_port));
      printf("(Name is : %s)\n", hp->h_name);
      printf("Disconnected..\n");
      FD_CLR(psd, &allset);
      client[i] = -1;
      close(psd);
   }
}
void
reusePort(int s)
{
   int             one = 1;

   if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *) &one, sizeof(one)) == -1) {
      printf("error in setsockopt,SO_REUSEPORT \n");
      exit(-1);
   }
}