Sending file through socket goes wrong C

Question

I'm on Windows. I try to send a file from client to server. It works when the server and client are on the same machine. But when I move the client to another machine, the server creates the desired file but fails to copy the client file. I don't understand why it works when server and client are on the same machine but when I move the client to another machine it doesn't.

How can I make my program work so that I can copy a file from client to server?

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); 
if (r == SOCKET_ERROR)
{
    printf("Client disconnected\n");
    break;
}

char buf[BUFSIZ];
size_t size = BUFSIZ;
                                        
FILE* copyFile;
fopen_s(&copyFile, ch, "wb");

while (size == BUFSIZ)
{
    recv(s, buf, BUFSIZ, 0);
    if (strncmp(buf, "exit", 10) == 0)
    {
        break;
    }
    size = fwrite(buf, 1, BUFSIZ, copyFile);
}
fclose(copyFile);

Client:

char c[70];
res = recv(ClientSocket, c, 70, 0);
if (res == SOCKET_ERROR)
{
    printf("Server disconeccted\n");
    break;
}

char buf[BUFSIZ];
size_t size = BUFSIZ;

FILE* originalFile;
fopen_s(&originalFile, c, "rb");

while (size == BUFSIZ)
{
    size = fread(buf, 1, BUFSIZ, originalFile);
    send(ClientSocket, buf, BUFSIZ, 0);
}
send(ClientSocket, "exit", 10, 0);
fclose(originalFile);