[gpderetta]

> UDP is streams in the very classical definition

What do you mean exactly? UDP is not a stream protocol, it is an unreliable datagram one. A single read will return exactly one UDP datagram.

It is TCP where a read will return incremental data which is not necessarily aligned to what the other end wrote.

Of course QUIC builds a reliable stream abstraction on top of it, but that's not different from TCP.

[friendzis]

In the classical definition stream is "sequence of data elements", without any additional guarantees. In this context TCP is stream transformer/filter: stream of "raw" packets is transformed into payload stream.

> What do you mean exactly? UDP is not a stream protocol, it is an unreliable datagram one. A single read will return exactly one UDP datagram.

This is exactly what makes UDP a stream of datagrams. Data is defined over one single UDP datagram - UDP gives exactly zero guarantees about data across datagram boundaries. There is no first, there is no last, there is no next/previous datagram, there no guarantees and expectations whether more datagrams will follow.

> Of course QUIC builds a reliable stream abstraction on top of it, but that's not different from TCP.

Key word "reliable", which is subset of streams. In goes stream of datagrams, out goes ordered (and otherwise identified) stream of bytes. Reading your comment it seems that you equate "stream" with "asynchronously fetched buffer" meaning from C++ and others, which is a stricter definition of streams.

[gpderetta]

I never heard of UDP defined as a stream (of packets), and it collides with the canonical definition of stream protocols from UNIX, BSD sockets, and the IP stack.

[friendzis]

No, it does not collide with "canonical" (colloquial, I'd say) definition of streams, when you think about it. It's only a matter of guarantees on a stream. It is not buffered reads/writes that make a stream.

I can take a bunch of XMLs, "stream" them into a TCP socket on one end, feed that socket to "XML stream processing library" on another end and... Watch it blow up, because apparently the only streamy thing about the library is that it can handle asynchronously filled buffer, but will nevertheless blow up if fed anything but a single well-formed xml ¯\_(ツ)_/¯

[gpderetta]

It is not colloquial when talking about network protocols. From socket(2):

          SOCK_STREAM
              Provides sequenced, reliable, two-way, connection-based
              byte streams.  An out-of-band data transmission mechanism
              may be supported.

Not sure what your reference to buffering or async buffers and XML has to do with the topic.

[friendzis]

Here you go, right in the documentation you get that TCP streams are streams with additional qualifiers. Not simply streams. The whole thing we are arguing about: TCP streams are subset of streams.

> Not sure what your reference to buffering or async buffers and XML has to do with the topic. An illustrative point for what happens when assumptions from a contrived case are applied on a more relaxed case.