/* dglistener2.c UDP "server" skeleton */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define MAXBUFLEN 2000
#define MAXHOSTNAMELEN 60
#define MAXPEERS 80

/* compare two addresses */
#define sameaddr(a, b) ( (a.sin_port == b.sin_port) && \
						 (a.sin_addr.s_addr == b.sin_addr.s_addr) )

/* this macro can be used to check errors, see server.c for examples */
#define ERRORCHECK(var, value, command) if (var == value) {     \
			perror(command);    \
			exit(1);            \
		}

int main(int argc, char *argv[])
{
	int sock;
	struct sockaddr_in own_addr;    /* my address information */
	struct sockaddr_in remote_addr; /* connector's address information */
	struct sockaddr_in addresses[MAXPEERS];
	char knownhosts[MAXPEERS*MAXHOSTNAMELEN] = "";
	char newhost[MAXHOSTNAMELEN];
	char hello[MAXHOSTNAMELEN] = "Hello\n";
	int knownpeers = 0, i;
	int nbytes;
	char buf[MAXBUFLEN];
	fd_set read_fds, orig_fds;
	int fdmax;
	int port = 54321;      /* default port */
	int stat;
	unsigned int sin_size = sizeof(struct sockaddr_in);

	/* port as optional parameter */
	if (argc > 1)
		port = atoi(argv[1]);

	/* socket */
	sock = socket(AF_INET, SOCK_DGRAM, 0);
	ERRORCHECK(sock, -1, "socket");


	/* bind to my address */
	own_addr.sin_family = AF_INET;  
	own_addr.sin_port = htons(port);
	own_addr.sin_addr.s_addr = INADDR_ANY;
	memset(&(own_addr.sin_zero), '\0', 8);

	stat = bind(sock, (struct sockaddr *)&own_addr, sin_size);
	ERRORCHECK(stat, -1, "bind");

	/* fd vector dor select */
	FD_ZERO(&orig_fds);
	/* insert socket and stdin */
	FD_SET(sock, &orig_fds);
	FD_SET(STDIN_FILENO, &orig_fds);
	fdmax = (sock < STDIN_FILENO) ? STDIN_FILENO : sock;

	/* copy is used for select() */
	FD_ZERO(&read_fds);

	while(strncmp(hello, "quit", 4)) {

		/* 10 seconds */
		struct timeval wt;
		wt.tv_sec = 10;
		wt.tv_usec = 0;

		/* copy tempory set */
		read_fds = orig_fds;

		/* use NULL instead of &wt to wait forever (not print .'s) */
		stat = select(fdmax+1, &read_fds, NULL, NULL, &wt);
		ERRORCHECK(stat, -1, "select");

		/* is socket ready for revcfrom? */
		if (FD_ISSET(sock, &read_fds)) {

			nbytes=recvfrom(sock, buf, MAXBUFLEN-1, 0,
							(struct sockaddr *)&remote_addr, &sin_size);
			ERRORCHECK(nbytes, -1, "recvfrom");

			/* check whether we have stored address already */
			/* in real-life application we should use hash */
			for (i = 0; i < knownpeers; i++)
				if (sameaddr(remote_addr, addresses[i]))
					break;

			if (i < knownpeers)
				printf("Old address\n");
			else {
				/* store new address */
				printf("New address\n");
				addresses[knownpeers++] = remote_addr;	/* sockaddr array */
				sprintf(newhost, " %s:%d ",				/* string of hosts */
						inet_ntoa(remote_addr.sin_addr),
						ntohs(remote_addr.sin_port));
				strcat(knownhosts, newhost);
			}

			printf("got message from %s, port %d\n",
				   inet_ntoa(remote_addr.sin_addr),
				   ntohs(remote_addr.sin_port));

			printf("message is %d bytes long\n",nbytes);
			buf[nbytes] = '\0';
			printf("message contains \"%s\"\n",buf);

			/* return by a message of hello text and list of known hosts */

			sprintf(buf, "%s\nKnown hosts: %s\n", hello, knownhosts);

			nbytes = sendto(sock, buf, strlen(buf), 0,
							(struct sockaddr *)&remote_addr, sin_size);
			ERRORCHECK(nbytes, -1, "sendto");

			printf("Sent:%s\n", buf);

		} /* if FD_ISSET(sock */

		/* if stdin is ready for read */
		if (FD_ISSET(STDIN_FILENO, &read_fds)) {
			/* read new hello text */
			fgets(hello, MAXHOSTNAMELEN, stdin);
		}

		printf(".\n");

	} /* while */

	close(sock);

	return 0;
}