[Python-Dev] Questionable TCP server example

[Antoine Pitrou]

On Thu, 23 Apr 2015 09:21:11 +0200
Andrea Griffini <agriff at tin.it> wrote:
> It's not the first time someone is confused by the server example of
> 
> https://docs.python.org/3/library/socketserver.html
> 
> where the receiving side is not making a loop over recv.

This is a trivial example indeed. If you think something more realistic
yet simple is desirable, we welcome contributions :-) You can take a
look at https://docs.python.org/devguide/ to get started.

> Moreover the documentation contains a misleading description of what really
> happens:
> 
> "The difference is that the readline() call in the second handler will call
> recv() multiple times until it encounters a newline character, while the
> single recv() call in the first handler will just return what has been sent
> from the client in one sendall() call."
> 
> Unless I'm missing something there's no way to know client side when all
> data sent by "sendall" has been received (TCP stream protocol doesn't have
> message boundaries) and the `recv` based code doesn't handle neither
> fragmentation nor clients that send more than 1024 bytes.

Indeed, the quoted paragraph is wrong.

> Am I missing something or that is indeed an example of how NOT to write a
> socket-based server?

The problem is coming up with an example that reflects better practices
while being simple enough :-)

Regards

Antoine.