/* 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>

#define DATA 1
#define ACK  2

#define NORMAL 		0
#define LOSEODD 	1
#define LOSEEVEN 	2

struct Msg {
	struct 	sockaddr_in dst;
	struct 	sockaddr_in src;
	char 	msgtype;
	char    buf[80];
	char	alternating_bit; }

help_msg()
{
	printf("format: channel -[doe]\n");
	printf("        option: d set debug on\n");
	printf("        option: o lose every other messages (odd number ones)\n");
	printf("        option: e lose every other messages (even number ones)\n");
}

void printsockaddr(struct sockaddr_in *arg)
{
    struct hostent *hp;
    printf("  sockaddr_in: ");
    printf("Domain=%d, ", arg->sin_family);
    hp=gethostbyaddr((const char *)&(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));
}


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

	int n;
	struct Msg m;
	extern char *optarg;
	extern int   optind;
	int option_exist = 0;
	int c;
	int counter = 1;
	int length;
	int flag = 1;
	int behavior = NORMAL;
	int debug = 0;

	/* process command line args */
	while ((c=getopt(argc,argv,"deo")) != EOF)
	{
		option_exist = 1;
		switch(c)
		{
		case 'o':
			behavior = LOSEODD;
			printf("Channel will lose odd numbered messages. (1,3,5)\n");
			break;
		case 'e':
			behavior = LOSEEVEN;
			printf("Channel will lose even numbered messages. (2,4,6)\n");
			break;

		case 'd':
		   debug = 1;
			printf("set debug mode on\n");
			break;
		case '?':
			help_msg();
			exit (1);
		default:
			fprintf (stderr, "unrecognized arg >%s<\n", optarg);
			help_msg();
			exit (1);
		}
	}

	/* 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));

	while (flag) {
		n = recv(sock, &m, sizeof(m), 0);
		if (n < 0) perror("receiving datagram message");
		printf("number of bytes received=%d\n", n);
		printf("m.msgtype=%d\n", m.msgtype);
		if (m.msgtype == DATA) printf("\treceived data msg=%s\n", m.buf);
		if (m.msgtype == ACK) printf("\treceived ack msg\n");
		printf("\talternating bit is %d\n", m.alternating_bit);
		m.dst.sin_family = AF_INET;
		if (debug) {
      	printsockaddr(&m.dst); 
      }
		if (behavior == LOSEODD && counter%2 != 0) {
			printf("lose odd number message, msg #%d\n", counter);
		} else if (behavior == LOSEEVEN && counter%2 ==0) {
			printf("lose even number message, msg #%d\n", counter);
		} else {
		if (sendto(sock, &m, n, 0, &m.dst, sizeof(m.dst))<0)
			perror("relay datagram message");
		}
		counter++;
	}
	close(sock);
}