// UDP Echo Client

#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#define SERVER_UDP_PORT         5000
#define MAXLEN                  4096
#define DEFLEN                  64

long delay(struct timeval t1, struct timeval t2)
{
        long d;
        d = (t2.tv_sec - t1.tv_sec) * 1000;
        d += ((t2.tv_usec - t1.tv_usec + 500) / 1000);
        return(d);
}
int main(int argc, char **argv)
{
       	int     data_size = DEFLEN, port = SERVER_UDP_PORT;
	int     i, j, sd, server_len;
       	char    *pname, *host, rbuf[MAXLEN], sbuf[MAXLEN];
       	struct  hostent         *hp;
       	struct  sockaddr_in     server;
       	struct  timeval         start, end;
	unsigned long address;

       	pname = argv[0];
       	argc--;
       	argv++;
       	if (argc > 0 && (strcmp(*argv, "-s") == 0)) {
       		if (--argc > 0 && (data_size = atoi(*++argv))) {
               	      argc--;
                     argv++;
               }
               else {
               	      fprintf(stderr,
                     "Usage: %s [-s data_size] host [port]\n", pname);
                     exit(1);
		}
        }
        if (argc > 0) {
                host = *argv;
                if (--argc > 0)
                        port = atoi(*++argv);
        }


	else {
		fprintf(stderr,
                "Usage: %s [-s data_size] host [port]\n", pname);
                exit(1);
	}

	if ((sd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
                fprintf(stderr, "Can't create a socket\n");
                exit(1);
        }

        bzero((char *)&server, sizeof(server));
        server.sin_family = AF_INET;
        server.sin_port = htons(port);
        if ((hp = gethostbyname(host)) == NULL) {
                fprintf(stderr, "Can't get server's IP address\n");
                exit(1);
        }
        bcopy(hp->h_addr, (char *) &server.sin_addr, hp->h_length);

	if (data_size > MAXLEN) {
                fprintf(stderr, "Data is too big\n");
                exit(1);
        }
	for (i = 0; i < data_size; i++) {
                j = (i < 26) ? i : i % 26;
                sbuf[i] = 'a' + j;
        } // construct data to send to the server
        gettimeofday(&start, NULL); /* start delay measurement */
	server_len = sizeof(server);
        if (sendto(sd, sbuf, data_size, 0, (struct sockaddr *)
                &server, server_len) == -1) {
                fprintf(stderr, "sendto error\n");
                exit(1);
        }
	if (recvfrom(sd, rbuf, MAXLEN, 0, (struct sockaddr *)
                &server, &server_len) < 0) {
                fprintf(stderr, "recvfrom error\n");
                exit(1);
        }
        gettimeofday(&end, NULL); /* end delay measurement */
        if (strncmp(sbuf, rbuf, data_size) != 0)
                printf("Data is corrupted\n");
        close(sd);
        return(0);
}