select.select and socket.setblocking

[Hendrik van Rooyen]

"Francesco Bochicchio" <bo.. at virgilio.it> wrote:

> but then, IIRC TCP guarantees that the packet is fully received by 
> hand-shaking at transport level between sender and receiver. Ad once the 
> packet is fully in the receiver buffer, why should recv choose to give
> back to the application only a piece of it?

This depends a lot on the definition of "package" - 

At the TCP/IP level, the protocol is quite complex - there 
are all sorts of info flowing back and forth, telling the 
transmitter how much space the receiver has available.
So your "record" or "package" could be split up...

But it gets worse, or better, depending on your point of view:

At the ethernet level, a packet is less than 1.5k - so if your
record is longer, it can also be split up - OTOH, if it all
fits into one ethernet packet, there is every chance that
it won't be split up, unless you send a lot of them in a row,
without waiting for a response - if you are running something that
sends a small request and listens for a small answer, then you
will probably never see a record split - but if you run a kind
of sliding window protocol that streams a lot of data (even in
small packets) then sooner or later one of them will be partly
delivered...

- Hendrik