/* dgtalker5.c -- a datagram sending skeleton */

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

#define MAXBUFLEN 2000

/* 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 remote_addr; /* connector's address information */
	struct sockaddr_in own_addr;
	struct hostent *he;
	int nbytes;
	char buf[MAXBUFLEN];
	int remoteport = 1;      /* no default ports */
	unsigned int sin_size = sizeof(struct sockaddr);
	int stat;

	if (argc != 4) {
		fprintf(stderr,"usage: %s hostname remoteport message\n", argv[0]);
		exit(1);
	}

	he=gethostbyname(argv[1]);  /* get the host info */
	ERRORCHECK(he, NULL, "gethostbyname");

	remoteport = atoi(argv[2]);	/* sanity check needed */

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


	/* remote address struct */
	remote_addr.sin_family = AF_INET;
	remote_addr.sin_port = htons(remoteport);
	remote_addr.sin_addr = *((struct in_addr *)he->h_addr);
	memset(&(remote_addr.sin_zero), '\0', 8);

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

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

	/* send packet */
	nbytes=sendto(sock, argv[2], strlen(argv[2]), 0,
				  (struct sockaddr *)&remote_addr, sin_size);
	ERRORCHECK(nbytes, -1, "sendto");

	printf("sent %d bytes to %s\n", nbytes,
		   inet_ntoa(remote_addr.sin_addr));

	/* receive reply */
	/* this should time-out using select() in case of lost packet */
	nbytes=recvfrom(sock, buf, MAXBUFLEN-1, 0,
					(struct sockaddr *)&remote_addr, &sin_size);
	ERRORCHECK(nbytes, -1, "recvfrom");

	buf[nbytes] = '\0';

	printf("received %d bytes :\n%s\n.\n", nbytes, buf);

	/* Pause here only to demonstrate usage of ports */
	printf("Paused, press enter\n");
	getchar(); /* wait */

	close(sock);

	return 0;
}