Server/client program behaves different after adding code in C - c

Question

I'm on Windows. I have a server/client program that copies a file from client to server. Everthing works as expected until I add the code where I send the size of the file from client to server. When I remove the code it works fine again. The while() loop in my server normally loops 378 times the while() loop in my client also loops 378 times. After I add the code to send the file size the while() loop in my server loops 377 times, and that causes the failure. I don't get any errors but when I click on the copied file it doesn't show anything(because the server loops 377 instead of 378). I commented *** where the code is that I'm talking about. What is the cause of this and how can I solve it?
Edit: The server receives the size of the file successfully
functions:
int getSizeFile(FILE* file)
{
// get file size
FILE *f = file;
fseek(f, 0L, SEEK_END);
int sizeFile = ftell(f);
rewind(f);
return sizeFile;
}
static inline uint32_t ntohl_ch(char const* X)
{
uint32_t x; memcpy(&x, X, sizeof(x));
return ntohl(x);
}
server:
char ch[70];
printf("where do you want to save it(full path + name): ");
scanf_s("%s", ch, 70);
char c[70];
printf("which file you want to copy(full path + name): ");
scanf_s("%s", c, 70);
r = send(s, c, 70, 0); // B
if (r == SOCKET_ERROR)
{
printf("2 error: %d\n", WSAGetLastError);
}
FILE* copyFile;
fopen_s(&copyFile, ch, "wb");
if (copyFile == NULL)
{
printf("Error opening file\n");
}
char buf[BUFSIZE];
size_t size = BUFSIZE;
int counter = 0;
// *** receiving file size. This is the code
char b[8192];
r = recv(s, b, 8192, 0); // C
if (r == SOCKET_ERROR)
{
printf("error recv\n");
}
uint32_t test = ntohl_ch(&b[0]);
printf("%d\n", (int)test);
// *** Until here
while (1)
{
int res = recv(s, buf, BUFSIZE, 0);
if (res == SOCKET_ERROR)
{
printf("3 error %d\n", WSAGetLastError);
break;
}
size = fwrite(buf, 1, res, copyFile);
printf("size: %d\n", size);
printf("res: %d\n", res);
counter++;
printf("counter: %d\n", counter);
}
fclose(copyFile);
client:
char c[70];
res = recv(ClientSocket, c, 70, 0); // B
if (res == SOCKET_ERROR)
{
printf("Server disconeccted\n");
break;
}
FILE* originalFile;
fopen_s(&originalFile, c, "rb");
if (originalFile == NULL)
{
printf("Error opening file\n");
}
char buf[BUFSIZE];
size_t size = BUFSIZE;
int counter = 0;
// getting file size
int sizeFile = getSizeFile(originalFile);
// *** sending file size. This is the code
uint32_t num = htonl(sizeFile);
char* converted_num = (char*)#
res = send(ClientSocket, converted_num, sizeof(num), 0); // C
if (res == SOCKET_ERROR)
{
printf("error send\n");
}
// *** Until here
while (size == BUFSIZE)
{
size = fread(buf, 1, BUFSIZE, originalFile);
int r = send(ClientSocket, buf, size, 0);
if (r == SOCKET_ERROR)
{
printf("1 error: %d\n", WSAGetLastError);
break;
}
printf("size: %d\n", size);
printf("r: %d\n", r);
counter++;
printf("counter: %d\n", counter);
}
printf("out of while loop\n");
fclose(originalFile);