/* sender for internet datagram demo */
/* modification 9/20/93 with Louis Sanchez's bug fix */

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


/************************************************************
printsockaddr prints the contents of a sockaddr_in structure when
called with a pointer to such a structure.
************************************************************/


void printsockaddr(struct sockaddr_in *arg)
{
  struct hostent *hp;
  printf("  sockaddr_in: ");
  printf("Domain=%d, ", arg->sin_family);
  hp=gethostbyaddr(&(arg->sin_addr), sizeof(arg->sin_addr), AF_INET);
  printf("Hostname=%s, ", hp->h_name);
  printf("Port=%d, ", ntohs(arg->sin_port));
  printf("Address=%s,\n", inet_ntoa(arg->sin_addr));
}
help_msg()
{
	printf("format: idgs3 -[dn] hostname portno\n");
	printf("          option: n set the number of messages sent\n");
	printf("                  d set debug mode\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;
	int noOfMsgs;
	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 ((noOfMsgs = atoi(optarg)) < 1) noOfMsgs = 1;
			if (debug)
				printf("The number of messags to be sent = %d.\n", noOfMsgs);
			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;
	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(hp->h_addr, &to.sin_addr, hp->h_length);
	to.sin_family = AF_INET;
	to.sin_port = htons(toPort_no);

	/*send message */
	for (i=1; i<=noOfMsgs; i++) {
		sprintf(toBuf, "packet %d\n", i);
		if (sendto(sock, toBuf, strlen(toBuf), 0, &to, sizeof(to)) < 0) 
			perror("sending datagram message");
		n = recv(sock, fromBuf, 1024, flag);
		if (n < 0) perror("receiving datagram message");
		fromBuf[n] = 0; /* null terminate */
		printf("received %d bytes, msg=%s\n", n, fromBuf);
	}
	close(sock);
}