/* sender for internet datagram demo */
/* modification 9/20/93 with Louis Sanchez's bug fix */
/* The idgs uses stop-and-wait protocol, wait for ack before sending
 * next  data packet. 
*/

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>

#define ENDPACKET "end"

help_msg()
{
   printf("format: idgs -[dn] hostname portno\n");
   printf("          option: d set debug mode\n");
   printf("          option: n set number of messages sent\n");
}

main(argc, argv)
int argc;
char *argv[];
{
   int sock; 
   struct sockaddr_in to;
   struct sockaddr_in from;
   struct hostent *hp, *gethostbyname();

   int i;
   int n=1;
   int nBytesRcvd;
   char toBuf[1024];
   char fromBuf[1024];
   char hostname[64];
   extern char *optarg;
   extern int   optind;
   int option_exist = 0;
   int c;
   int debug = 0;
   char *rcv_name;  /* receiver's socket name */
   int toPort_no;
   int length;
   int flag;

   /* process command line args */
   while ((c=getopt(argc,argv,"dn:")) != EOF)
   {
      option_exist = 1;
      switch(c)
      {
      case 'd':
         debug = 1;
         if (debug)
            printf("turn on debug mode.\n");
         break;

      case 'n':
         if ((n = atoi(optarg)) < 1) n = 1;
         if (debug)
            printf("The number of msgs sent is set to %d\n", n);
         break;
      case '?':
         help_msg();
         exit (1);
      default:
         fprintf (stderr, "unrecognized arg >%s<\n", optarg);
         help_msg();
         exit (1);
      }
   }

   rcv_name = argv[optind++];
   if ((toPort_no = atoi(argv[optind])) < 1025) toPort_no = 1025;

   if (debug) printf("The receiver's host name is %s, port_no=%d\n", rcv_name, toPort_no);

   /* create socket from which to read */
   sock = socket(AF_INET, SOCK_DGRAM, 0);
   if (sock < 0) {
      perror("opening datagram socket");
      exit(1);
   }
   /* create name structure with wildcard using INADDR_ANY */
   from.sin_family = AF_INET;
   from.sin_addr.s_addr = INADDR_ANY;
   /* if the machine has multiple nic card, this accepts msgs from both */
   from.sin_port = 0;  
   /* port no. < 1024 IPPORT_RESERVED is for privillege process */
   /* here just initialized it, it will be assigned value after call */
   /* getsockname() */
   if (bind(sock, &from, sizeof(struct sockaddr_in))) {
      perror("binding name to datagram socket");
      exit(1);
   }
   length = sizeof(from);
   if (getsockname(sock, &from, &length)) {
      perror("getting socket name");
      exit(1);
   }
   /* Find assigned port value and print out. */
   printf("socket has port #%d\n", ntohs(from.sin_port));

   /* construct name of the socket to send to 
    * gethostbyname() returns a structure including the network address
    * of the specified host from /etc/hosts. The port number is taken from
    * the cmd line
    * create name structure for the UNIX domain socket 
    * use the name from cmd argument 
    */
   hp = gethostbyname(rcv_name);
   if (hp == 0) {
      fprintf(stderr, "%s: unknown host",rcv_name);
      exit(2);
   }
   /* bcopy is depreciated replaced with memcpy 
      note that order in the first two parameters are different 
       bcopy(hp->h_addr, &to.sin_addr, hp->h_length);
   */
   memcpy(&to.sin_addr, hp->h_addr, hp->h_length);
   to.sin_family = AF_INET;
   to.sin_port = htons(toPort_no);

   /*send message */
        for (i=0; i<n; i++) {
      sprintf(toBuf, "packet %d!\n", i);
      if (debug) printf("Sending msg: %s", toBuf);
      if (sendto(sock, toBuf, strlen(toBuf), 0, &to, sizeof(to)) < 0) 
         perror("sending datagram message");
      nBytesRcvd = recv(sock, fromBuf, 1024, 0);
      if (nBytesRcvd < 0) perror("receiving datagram message");
      fromBuf[nBytesRcvd] = 0; /* null terminate */
      if (debug) {
         printf("number of bytes received=%d\n", nBytesRcvd);
         printf("received ack msg=%s\n", fromBuf);
      }
   }
   close(sock);
}