No, your assumptions are wrong. My buffer is not 1024, and I am not sending it (as I stated, I CANNOT send it, I can't guess the contents of these packets). It is not that simple. The socket on my side is async, but that doesn't matter. I can't say what kind of socket the other program is using (I don't think that they use MFC at all). And code snippets won't help - it's a simple derivated socket which receives stuff and sends a small reply (and this reply does not contain garbage, nor is it 1024 bytes long). I can only say that these packages cannot come from my app. I neither can guess the contents of them (that would solve my problems, lol), nor do I send anything at that time (I only send sth. when I receive sth., and as I stated, I don't receive anything after a while... and even if I don't send anything at all these 1024 byte packages arrive at the other app).