[Python-Dev] PEP 3156 - Asynchronous IO Support Rebooted (original) (raw)

Guido van Rossum guido at python.org
Sat Jan 5 00:56:23 CET 2013

On Mon, Dec 24, 2012 at 2:58 PM, Glyph <glyph at twistedmatrix.com> wrote:

In my humble (but entirely, verifiably correct) opinion, thinking of this as a "default" is propagating a design error in the BSD sockets API. Datagram and stream sockets have radically different semantics. In Twisted, "dataReceived" and "datagramReceived" are different methods for a good reason. Again, it's very very easy to fall into the trap of thinking that a TCP segment is a datagram and writing all your application code as if it were. After all, it probably works over localhost most of the time! This difference in semantics mirrored by a difference in method naming has helped quite a few people grok the distinction between streaming and datagrams over the years; I think it would be a good idea if Tulip followed suit.

Suppose PEP 3156 / Tulip uses data_received() for streams and datagram_received() for datagram protocols (which seems reasonable enough), what API should a datagram transport have for sending datagrams? write_datagram() and write_datagram_list()?

(Given that the transport and protocol classes are different for datagrams, I suppose the create*() methods should also be different, rather than just having a type={SOCK_STREAM,SOCK_DATAGRAM} flag. But I can figure that out for myself. The naming and exact APIs for the client and server transport creation methods are in flux anyway.)

-- --Guido van Rossum (python.org/~guido)

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