UDP_Client.c

#include<stdio.h>
#include<string.h> 
#include<stdlib.h> 
#include<arpa/inet.h>
#include<sys/socket.h>

#define SERVER "127.0.0.1"
#define BUFLEN 503
#define PORT 8885

void die(char *s)
{
	perror(s);
	exit(1);
}
unsigned long fsize(char* file)
{
    FILE * f = fopen(file, "r");
    fseek(f, 0, SEEK_END);
    unsigned long len = (unsigned long)ftell(f);
    fclose(f);
    return len;
}

int main(void)
{
	struct sockaddr_in si_other;
	int s, i, slen=sizeof(si_other);
	char buf[BUFLEN];
	char message[BUFLEN];

	if ( (s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
	{
		die("socket");
	}

	memset((char *) &si_other, 0, sizeof(si_other));
	si_other.sin_family = AF_INET;
	si_other.sin_port = htons(PORT);
	
	if (inet_aton(SERVER , &si_other.sin_addr) == 0) 
	{
		fprintf(stderr, "inet_aton() failed\n");
		exit(1);
	}
	char fname[20];
	printf("Enter Filename with extension: ");
	scanf("%s",&fname);
	sendto(s, fname, 20 , 0 , (struct sockaddr *) &si_other, slen);

	memset(message,0,BUFLEN);
	unsigned long siz = fsize(fname);
	printf("%ld",(siz % BUFLEN));
	char str[10];
	sprintf(str, "%d", siz);
	sendto(s, str, 20 , 0 , (struct sockaddr *) &si_other, slen);
	
	FILE *f;
	f=fopen(fname,"rb");
	memset(message,0,BUFLEN);
	fread(message, BUFLEN,1,f);
	int itr =1;
	while(itr*BUFLEN<siz){
		if (sendto(s, message, BUFLEN , 0 , (struct sockaddr *) &si_other, slen)==-1)
		{
			die("sendto()");
		}
		memset(message,0,BUFLEN);
		fread(message, BUFLEN,1,f);
		itr++;
	}
	fread(message, (siz % BUFLEN),1,f);
	sendto(s, message, (siz % BUFLEN) , 0 , (struct sockaddr *) &si_other, slen);
	memset(message,0,BUFLEN);
	fclose(f);
	close(s);
	return 0;
}