/* receiver 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>
#include <arpa/inet.h>

#define ENDPACKET "end"

struct Message_header {
    char sender[10]; /* sender login */
    int sessionID; /* starting from 1 */
};
struct Pen_Message {
    struct Message_header header;
    unsigned char msg_type;
    unsigned char size;
    short x;
    short y;
} pen;

/************************************************************
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((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));
}



help_msg()
{
	printf("format: idgr\n");
}

main(argc, argv)
int argc;
char *argv[];
{
	int sock; 
	struct sockaddr_in from;
	int n, i;
	char toBuf[2048];
	char fromBuf[2048];
	int length;
	int flag = 1;

	/* create socket */
	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. < 2048 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));

	/* receive message */
	while (flag) {
		n = recvfrom(sock, &pen, sizeof(pen), 0, &from, &length);
		printf("sizeof(pen)=%d\n", sizeof(pen));
		if (n < 0) perror("receiving datagram message");
		printf("The no. of bytes received=%d\n", n);
   	/* receive pen message */
   	printf("receive pen message:\n");
   	printf("\t pen.header.sender = %s\n", pen.header.sender);
   	printf("\t pen.header.sessionID = %d\n", pen.header.sessionID);
   	printf("\t pen.msg_type = %d\n", pen.msg_type);
   	printf("\t pen.size = %d\n", pen.size);
   	printf("\t pen.x = %d\n", pen.x);
   	printf("\t pen.y = %d\n", pen.y);
	}
	close(sock);
}