PSI test v C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define BUFFER_MAX 1024
#define DATA_SIZE 1016

unsigned int File_size(char* fname){
FILE *fa = fopen(fname, "rb");
fseek(fa, 0, SEEK_END);
unsigned int fileSize = ftell(fa);
rewind(fa);
fclose(fa);
return fileSize;
}


int main (int argc, char* argv[]){
unsigned char packet_number_check;
unsigned int sent =0;
unsigned char packet_number =0;
unsigned int data = 0;
char arr[BUFFER_MAX];
unsigned int n = 348648;//File_size(argv[1]);

FILE *fa = fopen(argv[1], "rb");

arr[0] = (n >> 24) & 0xFF;
arr[1] = (n >> 16) & 0xFF;
arr[2] = (n >> 8) & 0xFF;
arr[3] = n & 0xFF;
strcpy((arr+4), argv[1]);
//**************************************************
//recieve
unsigned int recieved_n = (arr[0] << 24) + (arr[1] << 16) + (arr[2] << 8) + (arr[3]);
//printf("%s", &arr[4]);
FILE * fb = fopen("recieved.png", "wb");
fprintf(fb, "asdf");



while (sent <= n){
//**********************
//send
arr[0] = packet_number++;
for (int i =0; i<DATA_SIZE; ++i){
arr[i+1] = getc(fa);
}
sent += DATA_SIZE;

//**************
// recieve
//printf("%d %d\n", packet_number_check++, (unsigned char) arr[0]);
if (packet_number_check++ != (unsigned char) arr[0])
	printf("packet number check failed, %d, %d\n", packet_number_check,(unsigned char) arr[0]);
for (int i=0; i<DATA_SIZE; ++i){
if(data<=recieved_n){
printf("DONE\n");
goto end;
}
fprintf(fb, "%c", arr[i+1]);
data++;
}
end:
fclose(fa);
fclose(fb);

}


return 0;
}