DhtMessage

The KRPC message model and codec for the BitTorrent DHT: a pure-Kotlin port of the message-building and -parsing code spread across libtorrent's src/kademlia/node.cpp (incoming_request, the per-query response builders, and the single-bucket-refresh / ping query builders), find_data.cpp, get_peers.cpp, get_item.cpp, put_data.cpp and msg.cpp.

Every DHT packet is a bencoded dictionary with three or four top-level keys (BEP-5 "KRPC Protocol"):

• t: the transaction id, an opaque byte string (libtorrent uses 2 random bytes, see rpc_manager::invoke). The responder echoes it verbatim.

• y: the message type, either "q" query, "r" response or "e" error.

• v: an optional client-version string (not modelled here; libtorrent adds it at the transport layer).

• q + a: for a query, the query name and its argument dict.

• r: for a response, the response dict.

• e: for an error, the [code, message] list (incoming_error).

The argument/response dict for every query carries the sender's own node id under id (rpc_manager::add_our_id / node::incoming_request's add_our_id(reply)).

This file provides:

• a sealed DhtMessage hierarchy (Query/Response/ErrorMessage) with the typed argument/response payloads BEP-5/44/51 define,

• build*Query(...) and build*Response(...) helpers returning an editable Entry (ready for Bencode.encode), matching the e["y"]=…; e["a"][…]=… assembly in libtorrent, and

• DhtMessage.parse, the dual of verifyMessage: it reads a decoded BdecodeNode envelope back into a typed DhtMessage.

Reuses NodeId/Sha1Hash, DhtEndpoint/CompactNode (compact node info), ImmutableItem/MutableItem (BEP-44 values) and DhtKeySizes.

Inheritors