Module draft20 

MoQT client implementation for draft-20.

Each draft lives in its own top-level module with a complete, independent implementation: connection, endpoint state machine, event types, observer trait, and per-flow state machines (subscribe, fetch, publish, namespace, track status). No code is shared across drafts — each draft carries its own copy because wire-level differences would make a shared layer leaky.

Enable via the draft20 feature.

What changed from draft-19, in the places a caller can feel it

• FETCH was rebuilt (Section 10.13). The Fetch Type field, the Standalone and Joining Fetch structures and the whole joining mechanism are gone; the Track Namespace and Track Name are inline fields, and the range travels in the LOCATION_FILTER parameter. So Connection::fetch takes a parameter list where draft-19’s took four location varints, and joining_fetch / absolute_joining_fetch no longer exist. A fill fetch stream is what replaces them; see fill.
• FILL_PARAMETERS (0x23) is new (Section 10.2.15). Its presence on a SUBSCRIBE or a REQUEST_UPDATE asks the publisher to open a fill fetch stream — a unidirectional stream beginning with a FETCH_HEADER that carries the subscription’s Request ID. fill::FillParameters builds the parameter and Endpoint::fill_requested is what tells an arriving FETCH_HEADER apart from a fetch’s.
• PUBLISH_STATE_NOTIFY (0x22) is new (Section 10.10): a unilateral report from the publisher on a subscription’s stream, answered with nothing and not counted against MAX_REQUEST_UPDATES. It arrives as ClientEvent::PublishStateNotify.
• Ranges are inclusive at both ends (Sections 5.1.2, 10.13, 10.14). Draft-19’s fetch end was “the last Object, plus 1; or 0 to indicate the entire Group”; both conventions are deleted, and nothing in this module carries the arithmetic forward.
• INCLUDE_PROPERTIES (0x35) is new (Section 10.2.21): a uint8 opt-out from Track Properties on the responding OK, default 1.
• Three code points went: SUBSCRIPTION_ENDED (PUBLISH_DONE 0x3), VERSION_NEGOTIATION_FAILED (session 0x15) and INVALID_JOINING_REQUEST_ID (REQUEST_ERROR 0x32).
• There is still no version on the wire. The negotiated draft is the ALPN, moqt-20 on raw QUIC, exactly as on drafts 15 through 19.

Section numbers shifted from 10.10 on, and LOCATION_FILTER’s neighbours shifted with them. Every citation in this module is draft-20’s own.

Modules

connection

Outbound MoQT connection with MoQT framing over QUIC.

endpoint

Draft-20 MoQT endpoint.

event

Client event types emitted by a MoQT connection.

fetch

Fetch lifecycle state machine.

fill

Location filters and fill fetch streams, the two things draft-20 asks a subscriber to build that no earlier draft has.

namespace

Subscribe/Publish namespace state machines.

observer

Connection observer trait for receiving structured events.

publish

Publish lifecycle state machine.

session

MoQT session lifecycle management.

subscription

Subscription lifecycle state machine.

track_status

Track status lifecycle state machine.