tokio-xmpp: add option to split client

Adds an option to split the `tokio-xmpp::Client` into a Sender and
Receiver. To enable this, a client worker is added which drives the
stream in the background.

tokio-xmpp/ChangeLog

@@ -22,6 +22,7 @@ Version NEXT:
     * Changed:
       - Update hickory-dns to 0.26 (!671)
       - Drive the XMPP client stream in the background (!631)
+      - Add option to split XMPP client into read and write half (!631)
 
 Version 5.0.0:
 2025-10-28 pep <pep@bouah.net>

tokio-xmpp/src/client/iq.rs

@@ -252,7 +252,7 @@ impl IqResponseSink {
 }
 
 /// Utility struct to track IQ responses.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct IqResponseTracker {
     map: Arc<Mutex<IqMap>>,
     account_jid: Arc<Mutex<Option<BareJid>>>,

tokio-xmpp/src/client/mod.rs

@@ -4,18 +4,19 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+use crate::client::{receiver::ClientReceiver, sender::ClientSender};
+use crate::connect::ServerConnector;
+use crate::error::Error;
+use crate::event::Event;
+use crate::stanzastream::{self, StanzaStage, StanzaState, StanzaStream, StanzaToken};
+use crate::xmlstream::Timeouts;
+use crate::Stanza;
 use std::io;
-
+use std::sync::Arc;
+use tokio::sync::{mpsc, oneshot, Mutex};
+use tokio::task::JoinHandle;
 use xmpp_parsers::{jid::Jid, stream_features::StreamFeatures};
 
-use crate::{
-    connect::ServerConnector,
-    error::Error,
-    stanzastream::{StanzaStage, StanzaState, StanzaStream, StanzaToken},
-    xmlstream::Timeouts,
-    Stanza,
-};
-
 #[cfg(feature = "direct-tls")]
 use crate::connect::DirectTlsServerConnector;
 #[cfg(any(feature = "direct-tls", feature = "starttls", feature = "insecure-tcp"))]
@@ -27,10 +28,13 @@ use crate::connect::TcpServerConnector;
 
 mod iq;
 pub(crate) mod login;
+pub(crate) mod receiver;
+pub(crate) mod sender;
 mod stream;
-pub use login::auth;
+mod worker;
 
 pub use iq::{IqFailure, IqRequest, IqResponse, IqResponseToken};
+pub use login::auth;
 
 /// XMPP client connection and state
 ///
@@ -41,9 +45,19 @@ pub use iq::{IqFailure, IqRequest, IqResponse, IqResponseToken};
 /// used.
 #[derive(Debug)]
 pub struct Client {
-    stream: StanzaStream,
+    // Stanza receiver from the client worker
+    stanza_rx: mpsc::Receiver<Event>,
+    // Stanza sender to the StanzaStream
+    stream_tx: stanzastream::StanzaSender,
+    // Shutdown handle for the client worker
+    shutdown_tx: oneshot::Sender<()>,
+    // Client worker task
+    worker: JoinHandle<stanzastream::StanzaReceiver>,
+    // JID of the logged-in client
     bound_jid: Option<Jid>,
+    // Stream features of the currently connected stream
     features: Option<StreamFeatures>,
+    // Response tracker for IQs
     iq_response_tracker: iq::IqResponseTracker,
 }
 
@@ -72,7 +86,8 @@ impl Client {
     /// [`send_iq`][`Self::send_iq`], which allows awaiting the response.
     pub async fn send_stanza(&mut self, mut stanza: Stanza) -> Result<StanzaToken, io::Error> {
         stanza.ensure_id();
-        let mut token = self.stream.send(Box::new(stanza)).await;
+        let mut token = self.stream_tx.send(Box::new(stanza)).await;
+
         match token.wait_for(StanzaStage::Sent).await {
             // Queued < Sent, so it cannot be reached.
             Some(StanzaState::Queued) => unreachable!(),
@@ -93,13 +108,6 @@ impl Client {
     /// response. See also the documentation of [`IqResponseToken`] for more
     /// information on the behaviour of these tokens.
     ///
-    /// **Important**: Even though IQ responses are delivered through the
-    /// returned token (and never through the `Stream`), the
-    /// [`Stream`][`futures::Stream`]
-    /// implementation of the [`Client`] **must be polled** to make progress
-    /// on the stream and to process incoming stanzas and thus to deliver them
-    /// to the returned token.
-    ///
     /// **Note**: If an IQ response arrives after the `token` has been
     /// dropped (e.g. due to a timeout), it will be delivered through the
     /// `Stream` like any other stanza.
@@ -108,7 +116,8 @@ impl Client {
             // from is always None for a client
             None, to, req,
         );
-        let stanza_token = self.stream.send(Box::new(iq.into())).await;
+        let stanza_token = self.stream_tx.send(Box::new(iq.into())).await;
+
         token.set_stanza_token(stanza_token);
         token
     }
@@ -128,9 +137,42 @@ impl Client {
     /// This performs an orderly stream shutdown, ensuring that all resources
     /// are correctly cleaned up.
     pub async fn send_end(self) -> Result<(), Error> {
-        self.stream.close().await;
+        self.shutdown_tx.send(()).expect("ClientWorker crashed.");
+
+        let stream_rx = self.worker.await.unwrap();
+        let stream = StanzaStream::reunite(self.stream_tx, stream_rx);
+        stream.close().await;
+
         Ok(())
     }
+
+    /// Split the client into [`ClientSender`] and [`ClientReceiver`].
+    pub fn split(self) -> (ClientSender, ClientReceiver) {
+        let client = Arc::new(Mutex::new(self));
+
+        let sender = ClientSender(client.clone());
+        let receiver = ClientReceiver(client);
+
+        (sender, receiver)
+    }
+
+    /// Reunite a [`ClientSender`] and [`ClientReceiver`].
+    ///
+    /// # Panics
+    ///
+    /// This functions returns an error if the [`ClientSender`] and
+    /// [`ClientReceiver`] don't come from the same [`Client`].
+    pub fn reunite(sender: ClientSender, receiver: ClientReceiver) -> Self {
+        assert!(
+            Arc::ptr_eq(&sender.0, &receiver.0),
+            "Unrelated ClientSender and ClientReceiver passed to reunite."
+        );
+
+        drop(sender);
+
+        let inner = Arc::try_unwrap(receiver.0).expect("Failed to unwrap ClientReceiver Arc");
+        inner.into_inner()
+    }
 }
 
 #[cfg(feature = "direct-tls")]
@@ -220,11 +262,23 @@ impl Client {
         connector: C,
         timeouts: Timeouts,
     ) -> Self {
+        let stream = StanzaStream::new_c2s(connector, jid.into(), password.into(), timeouts, 16);
+        let (stream_tx, stream_rx) = stream.split();
+
+        let iq_response_tracker = iq::IqResponseTracker::new();
+        let (worker, shutdown_tx, stanza_rx) =
+            worker::ClientWorker::new(stream_rx, iq_response_tracker.clone(), 16);
+
+        let worker = tokio::task::spawn(async move { worker.run().await });
+
         Self {
-            stream: StanzaStream::new_c2s(connector, jid.into(), password.into(), timeouts, 16),
+            stream_tx,
+            stanza_rx,
+            worker,
+            shutdown_tx,
+            iq_response_tracker,
             bound_jid: None,
             features: None,
-            iq_response_tracker: iq::IqResponseTracker::new(),
         }
     }
 }

tokio-xmpp/src/client/receiver.rs

@@ -0,0 +1,48 @@
+// Copyright (c) 2025 xmpp-rs contributors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use crate::Client;
+use crate::Event;
+use core::{pin::Pin, task::Context};
+use futures::StreamExt;
+use futures::{task::Poll, Stream};
+use std::sync::Arc;
+use tokio::sync::Mutex;
+use xmpp_parsers::{jid::Jid, stream_features::StreamFeatures};
+
+/// Read half of a [`Client`](crate::Client).
+#[derive(Debug)]
+pub struct ClientReceiver(pub(super) Arc<Mutex<Client>>);
+
+impl ClientReceiver {
+    /// Return the bound JID.
+    ///
+    /// See the documentation of [`Client::bound_jid`](crate::Client::bound_jid) for more
+    /// information.
+    pub async fn bound_jid(&self) -> Option<Jid> {
+        self.0.lock().await.bound_jid.clone()
+    }
+
+    /// Return the received stream features.
+    ///
+    /// See the documentation of [`Client::get_stream_features`](crate::Client::get_stream_features)
+    /// for more information.
+    pub async fn get_stream_features(&self) -> Option<StreamFeatures> {
+        self.0.lock().await.features.clone()
+    }
+}
+
+impl Stream for ClientReceiver {
+    type Item = Event;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
+        let Ok(mut client) = self.0.try_lock() else {
+            return Poll::Pending;
+        };
+
+        client.poll_next_unpin(cx)
+    }
+}

tokio-xmpp/src/client/sender.rs

@@ -0,0 +1,35 @@
+// Copyright (c) 2025 xmpp-rs contributors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use crate::stanzastream::StanzaToken;
+use crate::IqRequest;
+use crate::IqResponseToken;
+use crate::Stanza;
+use std::io;
+use std::sync::Arc;
+use tokio::sync::Mutex;
+use xmpp_parsers::jid::Jid;
+
+/// Write half of a [`Client`](crate::Client).
+#[derive(Debug)]
+pub struct ClientSender(pub(super) Arc<Mutex<super::Client>>);
+
+impl ClientSender {
+    /// Send a stanza.
+    ///
+    /// See the documentation of [`Client::send_stanza`](crate::Client::send_stanza) for more
+    /// information.
+    pub async fn send_stanza(&self, stanza: Stanza) -> Result<StanzaToken, io::Error> {
+        self.0.lock().await.send_stanza(stanza).await
+    }
+
+    /// Send in iq.
+    ///
+    /// See the documentation of [`Client::send_iq`](crate::Client::send_iq) for more information.
+    pub async fn send_iq(&self, to: Option<Jid>, req: IqRequest) -> IqResponseToken {
+        self.0.lock().await.send_iq(to, req).await
+    }
+}

tokio-xmpp/src/client/stream.rs

@@ -4,15 +4,10 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-use core::ops::ControlFlow;
 use core::{pin::Pin, task::Context};
 use futures::{ready, task::Poll, Stream};
 
-use crate::{
-    client::Client,
-    stanzastream::{Event as StanzaStreamEvent, StreamEvent},
-    Event, Stanza,
-};
+use crate::{client::Client, Event};
 
 /// Incoming XMPP events
 ///
@@ -32,39 +27,21 @@ impl Stream for Client {
     ///
     /// ...for your client
     fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
-        loop {
-            return Poll::Ready(match ready!(Pin::new(&mut self.stream).poll_next(cx)) {
-                None => None,
-                Some(StanzaStreamEvent::Stanza(st)) => match st {
-                    Stanza::Iq(iq) => match self.iq_response_tracker.handle_iq(iq) {
-                        ControlFlow::Break(()) => continue,
-                        ControlFlow::Continue(iq) => Some(Event::Stanza(Stanza::Iq(iq))),
-                    },
-                    other => Some(Event::Stanza(other)),
-                },
-                Some(StanzaStreamEvent::Stream(StreamEvent::Reset {
-                    bound_jid,
-                    features,
-                })) => {
-                    self.features = Some(features.clone());
+        Poll::Ready(match ready!(self.stanza_rx.poll_recv(cx)) {
+            None => None,
+            Some(event) => {
+                if let Event::Online {
+                    ref bound_jid,
+                    ref features,
+                    ..
+                } = event
+                {
                     self.bound_jid = Some(bound_jid.clone());
-
-                    self.iq_response_tracker
-                        .set_account_jid(bound_jid.to_bare());
-
-                    Some(Event::Online {
-                        bound_jid,
-                        features,
-                        resumed: false,
-                    })
+                    self.features = Some(features.clone());
                 }
-                Some(StanzaStreamEvent::Stream(StreamEvent::Resumed)) => Some(Event::Online {
-                    bound_jid: self.bound_jid.as_ref().unwrap().clone(),
-                    features: self.features.as_ref().unwrap().clone(),
-                    resumed: true,
-                }),
-                Some(StanzaStreamEvent::Stream(StreamEvent::Suspended)) => continue,
-            });
-        }
+
+                Some(event)
+            }
+        })
     }
 }

tokio-xmpp/src/client/worker.rs

@@ -0,0 +1,105 @@
+// Copyright (c) 2025 xmpp-rs contributors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use crate::client::iq;
+use crate::stanzastream::StanzaReceiver;
+use crate::stanzastream::{Event as StanzaStreamEvent, StreamEvent};
+use crate::{Event, Stanza};
+use core::ops::ControlFlow;
+use futures::StreamExt;
+use tokio::sync::mpsc;
+use tokio::sync::oneshot;
+use xmpp_parsers::jid::Jid;
+use xmpp_parsers::stream_features::StreamFeatures;
+
+/// Worker to drive the [`crate::stanzastream`] of a client in the background and continue to
+/// acknowledge IQs, even when the client is not polled.
+pub struct ClientWorker {
+    // Receiver from the StanzaStream
+    stream_rx: StanzaReceiver,
+    // Sender to the client (worker-to-frontend)
+    stanza_w2f_tx: mpsc::Sender<Event>,
+    // Shutdown signal receiver from frontend
+    shutdown_rx: oneshot::Receiver<()>,
+    // JID of the logged-in client
+    bound_jid: Option<Jid>,
+    // Stream features of the currently connected stream
+    features: Option<StreamFeatures>,
+    // Response tracker for IQs
+    iq_response_tracker: iq::IqResponseTracker,
+}
+
+impl ClientWorker {
+    pub fn new(
+        stream_rx: StanzaReceiver,
+        iq_response_tracker: iq::IqResponseTracker,
+        depth: usize,
+    ) -> (Self, oneshot::Sender<()>, mpsc::Receiver<Event>) {
+        let (shutdown_tx, shutdown_rx) = oneshot::channel();
+
+        // worker-to-frontend connection
+        let (stanza_w2f_tx, stanza_w2f_rx) = mpsc::channel(depth);
+
+        let worker = Self {
+            stream_rx,
+            stanza_w2f_tx,
+            iq_response_tracker,
+            shutdown_rx,
+            bound_jid: None,
+            features: None,
+        };
+
+        (worker, shutdown_tx, stanza_w2f_rx)
+    }
+
+    pub async fn run(mut self) -> StanzaReceiver {
+        loop {
+            tokio::select! {
+                _ = &mut self.shutdown_rx => {
+                    return self.stream_rx;
+                }
+                Some(event) = self.stream_rx.next() => {
+                    self.handle_event(event).await;
+                }
+            }
+        }
+    }
+
+    async fn handle_event(&mut self, event: StanzaStreamEvent) {
+        let send_event = match event {
+            StanzaStreamEvent::Stanza(st) => match st {
+                Stanza::Iq(iq) => match self.iq_response_tracker.handle_iq(iq) {
+                    ControlFlow::Break(()) => return,
+                    ControlFlow::Continue(iq) => Event::Stanza(Stanza::Iq(iq)),
+                },
+                other => Event::Stanza(other),
+            },
+            StanzaStreamEvent::Stream(StreamEvent::Reset {
+                bound_jid,
+                features,
+            }) => {
+                self.iq_response_tracker
+                    .set_account_jid(bound_jid.to_bare());
+
+                Event::Online {
+                    bound_jid,
+                    features,
+                    resumed: false,
+                }
+            }
+            StanzaStreamEvent::Stream(StreamEvent::Resumed) => Event::Online {
+                bound_jid: self.bound_jid.as_ref().unwrap().clone(),
+                features: self.features.as_ref().unwrap().clone(),
+                resumed: true,
+            },
+            StanzaStreamEvent::Stream(StreamEvent::Suspended) => return,
+        };
+
+        let Ok(()) = self.stanza_w2f_tx.send(send_event).await else {
+            panic!("All clients have been dropped.");
+        };
+    }
+}

tokio-xmpp/src/lib.rs

@@ -128,7 +128,11 @@ pub use xso::{asxml::PrintRawXml, error::FromElementError};
 #[doc(inline)]
 /// Generic tokio_xmpp Error
 pub use crate::error::Error;
-pub use client::{auth as client_login, Client, IqFailure, IqRequest, IqResponse, IqResponseToken};
+pub use client::{
+    auth as client_login, receiver::ClientReceiver, sender::ClientSender, Client, IqFailure,
+    IqRequest, IqResponse, IqResponseToken,
+};
+
 #[cfg(feature = "insecure-tcp")]
 pub use component::Component;
 pub use event::{Event, Stanza};