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Real MQTT wiring for Bambu: connect, auto-detect v5/v3.1.1, request/reply

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Removes GenericPrinter::receive (two disconnected fire-and-forget stubs
that didn't actually give request/response) in favor of a real mechanism
in the new src/printer/bambu_mqtt.rs:

- BambuMqttSession wraps whichever rumqttc client a connection ended up
  using (v3.1.1's AsyncClient/EventLoop for BambuMQTT v1, v5's for
  BambuMQTT v2 - different types, different event/error shapes) behind
  one interface. `open()` respects ForceV1/ForceV2, and for Auto tries
  v5 first, falling back to v3.1.1 on any failure (see the module doc
  comment for why "any failure", not a precisely-matched version-
  rejection code - unverified against a live printer, no broker here to
  test against).
- Reuses BambuTls::build_connector (now pub(crate)) for rumqttc's TLS
  transport via TlsConfiguration::NativeConnector, instead of a second,
  separate TLS trust story - hence rumqttc now pulls in use-native-tls
  instead of its default rustls stack, so there's one TLS implementation
  in the binary, not two.
- request() publishes and waits (with a timeout) for a report whose
  sequence_id matches, correlated via a shared pending-request table
  that a spawned background task completes as reports arrive - the
  first real tokio::spawn in this crate, flagged as deferred since
  printer/mod.rs's very first doc comment; this is why it was deferred
  until now, and why it's needed now (polling the eventloop has to run
  continuously, independent of whatever call site is waiting).
- publish()/publish_raw() are the fire-and-forget half, for commands
  like gcode_line that only get acknowledged implicitly.

BambuPrinter::connect/send_gcode_line/publish now call the real session
instead of printing what they would do. Verified against 192.0.2.1 (a
reserved, never-routable test address): both AsyncClient/EventLoop pairs
actually attempt a real TCP connection and fail gracefully (network
timeout, not a panic) when nothing answers, and Auto genuinely attempts
both while ForceV1 skips straight to v3.1.1.
This commit is contained in:
octoturge
2026-09-05 21:04:39 +00:00
parent b352fd618d
commit 9643c8b685
6 changed files with 310 additions and 84 deletions
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src/printer/bambu_mqtt.rs
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//! The real MQTT wiring for Bambu printers - the piece `connect`/
//! `send_gcode_line` in `bambu.rs` used to just stub out with a
//! `println!`. Two things make this more than "call `publish`, get a
//! `String` back":
//!
//! 1. MQTT v3.1.1 (BambuMQTT v1) and MQTT v5 (BambuMQTT v2) are two
//! entirely separate rumqttc client types (`rumqttc::AsyncClient` vs
//! `rumqttc::v5::AsyncClient`) with different event/error types -
//! `BambuMqttClient` is the enum that hides which one a connection
//! ended up using, same pattern as `PrinterHandle` hides which vendor
//! struct you're holding.
//! 2. A response to a published request doesn't come back from that same
//! call - it arrives later, asynchronously, on a *subscription* to
//! `device/{sn}/report`, correlated only by matching `sequence_id`.
//! That needs: a background task continuously polling the connection
//! (rumqttc doesn't do this for you - nothing happens until you poll
//! the `EventLoop` yourself, repeatedly, forever), and a shared table
//! of "who's waiting for which `sequence_id`" that task completes as
//! reports arrive. This is the first real use of `tokio::spawn` in
//! this crate - flagged as deferred since `printer/mod.rs`'s very
//! first doc comment, and this is why: it only makes sense once there's
//! a long-running background job (polling forever) that has to run
//! independently of whatever call site is waiting on a response.
//!
//! Unverified against a live printer (no broker to test against here):
//! the exact `ConnectReturnCode`/error shape a real Bambu printer's
//! embedded broker gives when it doesn't understand MQTT v5's CONNECT at
//! all (rather than a clean version-rejection CONNACK) - `open()` below
//! treats *any* failure of the v5 attempt as "fall back to v3.1.1", not
//! just a precisely-matched version-rejection code, since a broker that
//! can't parse a v5 CONNECT packet may just drop the connection instead
//! of replying with one.
use std::collections::HashMap;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;
use std::time::Duration;
use rumqttc::v5::mqttbytes::v5::Packet as PacketV5;
use rumqttc::v5::mqttbytes::QoS as QoSV5;
use rumqttc::{Event, Packet, QoS, Transport, TlsConfiguration};
use serde_json::Value;
use tokio::sync::{oneshot, Mutex};
use super::bambu::BambuTls;
use super::PrinterError;
use super::BambuProtocolVersion;
/// Requests waiting on a report with a matching `sequence_id`. Shared
/// between whichever call registered one (in `request`) and the
/// background poll task that completes it when the report arrives.
type PendingTable = Arc<Mutex<HashMap<String, oneshot::Sender<Value>>>>;
const REQUEST_TIMEOUT: Duration = Duration::from_secs(10);
enum BambuMqttClient {
V1(rumqttc::AsyncClient),
V2(rumqttc::v5::AsyncClient),
}
/// One live MQTT connection to a Bambu printer - whichever protocol
/// version `open()` settled on.
pub struct BambuMqttSession {
client: BambuMqttClient,
pending: PendingTable,
sn: String,
next_sequence_id: AtomicU64,
}
impl BambuMqttSession {
/// `ForceV1`/`ForceV2` connect with that protocol directly. `Auto`
/// tries v5 first and falls back to v3.1.1 if that attempt fails -
/// see this module's doc comment for why "any failure", not just a
/// precisely-matched version-rejection code.
pub async fn open(
host: &str,
access_code: &str,
sn: &str,
tls: &BambuTls,
preference: super::bambu::BambuProtocolPreference,
) -> Result<(Self, BambuProtocolVersion), PrinterError> {
use super::bambu::BambuProtocolPreference as Pref;
match preference {
Pref::ForceV1 => {
let session = Self::open_v1(host, access_code, sn, tls).await?;
Ok((session, BambuProtocolVersion::V1))
}
Pref::ForceV2 => {
let session = Self::open_v2(host, access_code, sn, tls).await?;
Ok((session, BambuProtocolVersion::V2))
}
Pref::Auto => match Self::open_v2(host, access_code, sn, tls).await {
Ok(session) => Ok((session, BambuProtocolVersion::V2)),
Err(_) => {
let session = Self::open_v1(host, access_code, sn, tls).await?;
Ok((session, BambuProtocolVersion::V1))
}
},
}
}
async fn open_v1(host: &str, access_code: &str, sn: &str, tls: &BambuTls) -> Result<Self, PrinterError> {
let connector = tls.build_connector().map_err(|err| PrinterError(format!("TLS setup failed: {err}")))?;
let mut options = rumqttc::MqttOptions::new(format!("continuum-{sn}"), host, 8883);
options.set_credentials("bblp", access_code);
options.set_transport(Transport::tls_with_config(TlsConfiguration::NativeConnector(connector)));
options.set_keep_alive(Duration::from_secs(30));
let (client, mut event_loop) = rumqttc::AsyncClient::new(options, 10);
client
.subscribe(format!("device/{sn}/report"), QoS::AtMostOnce)
.await
.map_err(|err| PrinterError(format!("subscribe failed: {err}")))?;
// Nothing actually happens on the wire until the eventloop is
// polled - this first poll is what makes the TCP+TLS+CONNECT
// handshake happen, and its result is the only way to know
// whether it worked.
match event_loop.poll().await {
Ok(_) => {}
Err(err) => return Err(PrinterError(format!("MQTT v3.1.1 connect failed: {err}"))),
}
let pending: PendingTable = Arc::new(Mutex::new(HashMap::new()));
tokio::spawn(poll_loop_v1(event_loop, pending.clone()));
Ok(Self { client: BambuMqttClient::V1(client), pending, sn: sn.to_string(), next_sequence_id: AtomicU64::new(1) })
}
async fn open_v2(host: &str, access_code: &str, sn: &str, tls: &BambuTls) -> Result<Self, PrinterError> {
let connector = tls.build_connector().map_err(|err| PrinterError(format!("TLS setup failed: {err}")))?;
let mut options = rumqttc::v5::MqttOptions::new(format!("continuum-{sn}"), host, 8883);
options.set_credentials("bblp", access_code);
options.set_transport(Transport::tls_with_config(TlsConfiguration::NativeConnector(connector)));
options.set_keep_alive(Duration::from_secs(30));
let (client, mut event_loop) = rumqttc::v5::AsyncClient::new(options, 10);
client
.subscribe(format!("device/{sn}/report"), QoSV5::AtMostOnce)
.await
.map_err(|err| PrinterError(format!("subscribe failed: {err}")))?;
match event_loop.poll().await {
Ok(_) => {}
Err(err) => return Err(PrinterError(format!("MQTT v5 connect failed: {err}"))),
}
let pending: PendingTable = Arc::new(Mutex::new(HashMap::new()));
tokio::spawn(poll_loop_v2(event_loop, pending.clone()));
Ok(Self { client: BambuMqttClient::V2(client), pending, sn: sn.to_string(), next_sequence_id: AtomicU64::new(1) })
}
/// Publishes `body` under `device/{sn}/request`, wrapped as
/// `{category: body}` (Bambu's top-level key names the *category*,
/// e.g. "print"/"info" - `body`'s own `command` field says which
/// specific one), and waits up to `REQUEST_TIMEOUT` for a report
/// whose `sequence_id` matches. Overwrites whatever `sequence_id`
/// `body` already had (continuum-schema-instance fills it with an
/// empty placeholder, since it has no way to know a real one) with a
/// fresh one from this session's own counter.
pub async fn request(&self, category: &str, mut body: Value) -> Result<Value, PrinterError> {
let sequence_id = self.next_sequence_id.fetch_add(1, Ordering::Relaxed).to_string();
body["sequence_id"] = Value::String(sequence_id.clone());
let (tx, rx) = oneshot::channel();
self.pending.lock().await.insert(sequence_id.clone(), tx);
if let Err(err) = self.publish(category, &body).await {
self.pending.lock().await.remove(&sequence_id);
return Err(err);
}
match tokio::time::timeout(REQUEST_TIMEOUT, rx).await {
Ok(Ok(response)) => Ok(response),
Ok(Err(_)) => Err(PrinterError(format!("{} closed before replying", self.sn))),
Err(_) => {
self.pending.lock().await.remove(&sequence_id);
Err(PrinterError(format!("{} did not reply within {REQUEST_TIMEOUT:?}", self.sn)))
}
}
}
/// Publishes `body` under `device/{sn}/request`, wrapped as
/// `{category: body}`, without waiting for a reply - for commands
/// like `gcode_line` that only get acknowledged implicitly (the
/// printer just executes it), not answered directly.
pub async fn publish(&self, category: &str, body: &Value) -> Result<(), PrinterError> {
self.publish_raw(serde_json::json!({ category: body }).to_string()).await
}
/// Publishes an already-serialized payload under `device/{sn}/request`
/// as-is, with no category wrapping - the low-level primitive both
/// `publish` above and `GenericPrinter::publish` (a raw pass-through,
/// no envelope opinion at all) are built on.
pub async fn publish_raw(&self, payload: String) -> Result<(), PrinterError> {
let topic = format!("device/{}/request", self.sn);
match &self.client {
BambuMqttClient::V1(client) => client
.publish(topic, QoS::AtLeastOnce, false, payload)
.await
.map_err(|err| PrinterError(format!("publish failed: {err}"))),
BambuMqttClient::V2(client) => client
.publish(topic, QoSV5::AtLeastOnce, false, payload)
.await
.map_err(|err| PrinterError(format!("publish failed: {err}"))),
}
}
}
/// Runs forever, polling the v3.1.1 eventloop and completing pending
/// requests as matching reports arrive. Ends (silently) once the
/// connection is gone for good - dropping the `BambuMqttSession` drops
/// its `AsyncClient`, which is what eventually makes that happen.
async fn poll_loop_v1(mut event_loop: rumqttc::EventLoop, pending: PendingTable) {
loop {
match event_loop.poll().await {
Ok(Event::Incoming(Packet::Publish(publish))) => {
complete_pending(&pending, &publish.payload).await;
}
Ok(_) => {}
Err(_) => return,
}
}
}
async fn poll_loop_v2(mut event_loop: rumqttc::v5::EventLoop, pending: PendingTable) {
loop {
match event_loop.poll().await {
Ok(rumqttc::v5::Event::Incoming(PacketV5::Publish(publish))) => {
complete_pending(&pending, &publish.payload).await;
}
Ok(_) => {}
Err(_) => return,
}
}
}
/// Parses an incoming report and, if its `sequence_id` matches something
/// `request` is waiting on, hands it the parsed JSON. A report with no
/// `sequence_id`, or one nothing's waiting on (an unsolicited status
/// push, not a reply to anything), is silently ignored - most Bambu
/// reports aren't replies to a specific request at all.
async fn complete_pending(pending: &PendingTable, payload: &[u8]) {
let Ok(value) = serde_json::from_slice::<Value>(payload) else { return };
let Some(sequence_id) = find_sequence_id(&value) else { return };
if let Some(sender) = pending.lock().await.remove(&sequence_id) {
let _ = sender.send(value);
}
}
/// A report is `{category: {"sequence_id": "...", ...}}` - one key, same
/// shape as a request. Look inside whichever single category key is
/// present rather than requiring the caller to already know it.
fn find_sequence_id(report: &Value) -> Option<String> {
let object = report.as_object()?;
let (_, category_body) = object.iter().next()?;
category_body.get("sequence_id")?.as_str().map(str::to_string)
}