size of socket.recv buffer

[Locke]

The argument to recv is supposed to be the buffer, acording to the
documentation. But the doc doesnt say: buffer measured in what? Is it bytes?
Octets? (by the way, what is the diff between a byte and an octet?)

See, I am writing a pop3 client type thing, after requesting a message from
the server, my first s.recv tells me how long the message will be in octets.
So then I call s.recv again passing the number of octets as the argument to
s.recv. Shouldn't this download the entire message? What actually happens is
that it cuts off right in the middle of the message.

What's my problem? Is there an upper limit on what the buffer argument can
be to recv? Or does pop3 just refuse to send the whole message with one call
to recv? I don't think it is that, because what it sent me was like 600some
characters, which isnt a power of two or any other computer-ish number.

Thanks