const int _size=4096;
char _buf[_size];

FILE* file;
file = fopen(address.c_str(), "rb");
int BytesRead = 0;
while (!feof(file)) {
    ZeroMemory(_buf, _size);
    BytesRead = fread(_buf, 1, _size, file);
    if (BytesRead > 0) {
        send(_skt, _buf, BytesRead, 0); // send data
        cout << BytesRead << endl;
        ZeroMemory(_buf, _size);
        recv(_skt, _buf, _size, 0);     // receive SUCCESS
    }
}
send(_skt, "eof", 3, 0);            // send eof
fclose(file);
cout << "transmitting successful" << endl;