added Single Peer Connection support to Rust

livekit-api/Cargo.toml

@@ -36,6 +36,7 @@ __signal-client-async-compatible = [
     "dep:futures-util",
     "dep:isahc",
     "dep:livekit-runtime",
+    "dep:base64"
 ]
 
 

livekit-api/src/signal_client/mod.rs

@@ -22,10 +22,12 @@ use std::{
     time::{Duration, SystemTime, UNIX_EPOCH},
 };
 
+use base64::{engine::general_purpose::STANDARD as BASE64_STANDARD, Engine};
 use http::StatusCode;
 use livekit_protocol as proto;
 use livekit_runtime::{interval, sleep, Instant, JoinHandle};
 use parking_lot::Mutex;
+use prost::Message;
 use thiserror::Error;
 use tokio::sync::{mpsc, Mutex as AsyncMutex, RwLock as AsyncRwLock};
 
@@ -90,6 +92,8 @@ pub struct SignalOptions {
     pub auto_subscribe: bool,
     pub adaptive_stream: bool,
     pub sdk_options: SignalSdkOptions,
+    /// Enable single peer connection mode
+    pub single_peer_connection: bool,
 }
 
 impl Default for SignalOptions {
@@ -98,6 +102,7 @@ impl Default for SignalOptions {
             auto_subscribe: true,
             adaptive_stream: false,
             sdk_options: SignalSdkOptions::default(),
+            single_peer_connection: true,
         }
     }
 }
@@ -119,6 +124,8 @@ struct SignalInner {
     options: SignalOptions,
     join_response: proto::JoinResponse,
     request_id: AtomicU32,
+    /// Tracks whether single PC mode is active (v1 path succeeded)
+    single_pc_mode_active: bool,
 }
 
 pub struct SignalClient {
@@ -235,6 +242,12 @@ impl SignalClient {
     pub fn next_request_id(&self) -> u32 {
         self.inner.next_request_id().clone()
     }
+
+    /// Returns whether single peer connection mode is active.
+    /// This is determined by whether the /rtc/v1 path was used successfully.
+    pub fn is_single_pc_mode_active(&self) -> bool {
+        self.inner.is_single_pc_mode_active()
+    }
 }
 
 impl SignalInner {
@@ -247,20 +260,56 @@ impl SignalInner {
         proto::JoinResponse,
         mpsc::UnboundedReceiver<Box<proto::signal_response::Message>>,
     )> {
-        let lk_url = get_livekit_url(url, &options)?;
-
+        // Try v1 path first if single_peer_connection is enabled
+        let use_v1_path = options.single_peer_connection;
+        // For initial connection: reconnect=false, reconnect_reason=None, participant_sid=""
+        let lk_url = get_livekit_url(url, &options, use_v1_path, false, None, "")?;
         // Try to connect to the SignalClient
-        let (stream, mut events) = match SignalStream::connect(lk_url.clone(), token).await {
-            Ok(stream) => stream,
-            Err(err) => {
-                if let SignalError::TokenFormat = err {
-                    return Err(err);
+        let (stream, mut events, single_pc_mode_active) =
+            match SignalStream::connect(lk_url.clone(), token).await {
+                Ok((new_stream, stream_events)) => {
+                    log::debug!(
+                        "signal connection successful: path={}, single_pc_mode={}",
+                        if use_v1_path { "v1" } else { "v0" },
+                        use_v1_path
+                    );
+                    (new_stream, stream_events, use_v1_path)
                 }
-                // Connection failed, try to retrieve more information
-                Self::validate(lk_url).await?;
-                return Err(err);
-            }
-        };
+                Err(err) => {
+                    log::warn!(
+                        "signal connection failed on {} path: {:?}",
+                        if use_v1_path { "v1" } else { "v0" },
+                        err
+                    );
+
+                    if let SignalError::TokenFormat = err {
+                        return Err(err);
+                    }
+
+                    // If using v1 path and it failed, always try fallback to v0 path.
+                    // The v1 endpoint might not be available on older servers, and errors
+                    // can manifest as various HTTP status codes (404, 401, 403) or connection errors.
+                    if use_v1_path {
+                        let lk_url_v0 = get_livekit_url(url, &options, false, false, None, "")?;
+                        log::warn!("v1 path failed, falling back to v0 path");
+                        match SignalStream::connect(lk_url_v0.clone(), token).await {
+                            Ok((new_stream, stream_events)) => (new_stream, stream_events, false),
+                            Err(err) => {
+                                log::error!("v0 fallback also failed: {:?}", err);
+                                if let SignalError::TokenFormat = err {
+                                    return Err(err);
+                                }
+                                Self::validate(lk_url_v0).await?;
+                                return Err(err);
+                            }
+                        }
+                    } else {
+                        // Connection failed on v0 path, try to retrieve more information
+                        Self::validate(lk_url).await?;
+                        return Err(err);
+                    }
+                }
+            };
 
         let join_response = get_join_response(&mut events).await?;
 
@@ -274,6 +323,7 @@ impl SignalInner {
             url: url.to_string(),
             join_response: join_response.clone(),
             request_id: AtomicU32::new(1),
+            single_pc_mode_active,
         });
 
         Ok((inner, join_response, events))
@@ -297,6 +347,11 @@ impl SignalInner {
         Ok(())
     }
 
+    /// Returns whether single peer connection mode is active
+    pub fn is_single_pc_mode_active(&self) -> bool {
+        self.single_pc_mode_active
+    }
+
     /// Restart is called when trying to resume the room (RtcSession resume)
     pub async fn restart(
         self: &Arc<Self>,
@@ -315,8 +370,13 @@ impl SignalInner {
         let sid = &self.join_response.participant.as_ref().unwrap().sid;
         let token = self.token.lock().clone();
 
-        let mut lk_url = get_livekit_url(&self.url, &self.options).unwrap();
-        lk_url.query_pairs_mut().append_pair("reconnect", "1").append_pair("sid", sid);
+        // Use the same path that succeeded during initial connection
+        // For reconnects: reconnect=true, participant_sid=sid
+        // For v1 path: reconnect and sid are encoded in the join_request protobuf
+        // For v0 path: reconnect and sid are added as separate query parameters
+        let lk_url =
+            get_livekit_url(&self.url, &self.options, self.single_pc_mode_active, true, None, sid)
+                .unwrap();
 
         let (new_stream, mut events) = SignalStream::connect(lk_url, &token).await?;
         let reconnect_response = get_reconnect_response(&mut events).await?;
@@ -459,7 +519,78 @@ fn is_queuable(signal: &proto::signal_request::Message) -> bool {
     )
 }
 
-fn get_livekit_url(url: &str, options: &SignalOptions) -> SignalResult<url::Url> {
+/// Create the base64-encoded WrappedJoinRequest parameter required for v1 path
+///
+/// Parameters:
+/// - options: SignalOptions containing auto_subscribe, adaptive_stream, etc.
+/// - reconnect: true if this is a reconnection attempt
+/// - participant_sid: the participant SID (only used during reconnection)
+fn create_join_request_param(
+    options: &SignalOptions,
+    reconnect: bool,
+    reconnect_reason: Option<i32>,
+    participant_sid: &str,
+) -> String {
+    let connection_settings = proto::ConnectionSettings {
+        auto_subscribe: options.auto_subscribe,
+        adaptive_stream: options.adaptive_stream,
+        ..Default::default()
+    };
+
+    let client_info = proto::ClientInfo {
+        sdk: proto::client_info::Sdk::Rust as i32,
+        version: options.sdk_options.sdk_version.clone().unwrap_or_default(),
+        protocol: PROTOCOL_VERSION as i32,
+        os: std::env::consts::OS.to_string(),
+        ..Default::default()
+    };
+
+    let mut join_request = proto::JoinRequest {
+        client_info: Some(client_info),
+        connection_settings: Some(connection_settings),
+        reconnect,
+        ..Default::default()
+    };
+
+    // Only set participant_sid if non-empty (for reconnects)
+    if !participant_sid.is_empty() {
+        join_request.participant_sid = participant_sid.to_string();
+    }
+
+    // Only set reconnect_reason if provided
+    if let Some(reason) = reconnect_reason {
+        join_request.reconnect_reason = reason;
+    }
+
+    // Serialize JoinRequest to bytes
+    let join_request_bytes = join_request.encode_to_vec();
+
+    // Create WrappedJoinRequest (JS doesn't explicitly set compression, so default is NONE)
+    let wrapped_join_request =
+        proto::WrappedJoinRequest { join_request: join_request_bytes, ..Default::default() };
+
+    // Serialize WrappedJoinRequest to bytes and base64 encode
+    let wrapped_bytes = wrapped_join_request.encode_to_vec();
+    BASE64_STANDARD.encode(&wrapped_bytes)
+}
+
+/// Build the LiveKit WebSocket URL for connection
+///
+/// Parameters:
+/// - url: the base server URL
+/// - options: SignalOptions
+/// - use_v1_path: if true, use /rtc/v1 (single PC mode), otherwise /rtc (dual PC mode)
+/// - reconnect: true if this is a reconnection attempt
+/// - reconnect_reason: reason for reconnection (only used when reconnect=true)
+/// - participant_sid: the participant SID (only used during reconnection)
+fn get_livekit_url(
+    url: &str,
+    options: &SignalOptions,
+    use_v1_path: bool,
+    reconnect: bool,
+    reconnect_reason: Option<i32>,
+    participant_sid: &str,
+) -> SignalResult<url::Url> {
     let mut lk_url = url::Url::parse(url).map_err(|err| SignalError::UrlParse(err.to_string()))?;
 
     if !lk_url.has_host() {
@@ -477,26 +608,46 @@ fn get_livekit_url(url: &str, options: &SignalOptions) -> SignalResult<url::Url>
 
     if let Ok(mut segs) = lk_url.path_segments_mut() {
         segs.push("rtc");
+        if use_v1_path {
+            segs.push("v1");
+        }
     }
 
-    lk_url
-        .query_pairs_mut()
-        .append_pair("sdk", options.sdk_options.sdk.as_str())
-        .append_pair("protocol", PROTOCOL_VERSION.to_string().as_str())
-        .append_pair("auto_subscribe", if options.auto_subscribe { "1" } else { "0" })
-        .append_pair("adaptive_stream", if options.adaptive_stream { "1" } else { "0" });
+    if use_v1_path {
+        // For v1 path (single PC mode): only join_request param
+        // All other info (sdk, protocol, auto_subscribe, etc.) is inside the JoinRequest protobuf
+        let join_request_param =
+            create_join_request_param(options, reconnect, reconnect_reason, participant_sid);
+        lk_url.query_pairs_mut().append_pair("join_request", &join_request_param);
+    } else {
+        // For v0 path (dual PC mode): use URL query parameters
+        lk_url
+            .query_pairs_mut()
+            .append_pair("sdk", options.sdk_options.sdk.as_str())
+            .append_pair("protocol", PROTOCOL_VERSION.to_string().as_str())
+            .append_pair("auto_subscribe", if options.auto_subscribe { "1" } else { "0" })
+            .append_pair("adaptive_stream", if options.adaptive_stream { "1" } else { "0" });
+
+        if let Some(sdk_version) = &options.sdk_options.sdk_version {
+            lk_url.query_pairs_mut().append_pair("version", sdk_version.as_str());
+        }
 
-    if let Some(sdk_version) = &options.sdk_options.sdk_version {
-        lk_url.query_pairs_mut().append_pair("version", sdk_version.as_str());
+        // For reconnects in v0 path, add reconnect and sid as separate query parameters
+        if reconnect {
+            lk_url
+                .query_pairs_mut()
+                .append_pair("reconnect", "1")
+                .append_pair("sid", participant_sid);
+        }
     }
 
     Ok(lk_url)
 }
 
-/// Convert a WebSocket URL (with /rtc path) to the validate endpoint URL
+/// Convert a WebSocket URL (with /rtc or /rtc/v1 path) to the validate endpoint URL
 fn get_validate_url(mut ws_url: url::Url) -> url::Url {
     ws_url.set_scheme(if ws_url.scheme() == "wss" { "https" } else { "http" }).unwrap();
-    // ws_url already has /rtc from get_livekit_url, so only append /validate
+    // ws_url already has /rtc or /rtc/v1 from get_livekit_url, so only append /validate
     if let Ok(mut segs) = ws_url.path_segments_mut() {
         segs.push("validate");
     }
@@ -545,18 +696,32 @@ mod tests {
     fn livekit_url_test() {
         let io = SignalOptions::default();
 
-        assert!(get_livekit_url("localhost:7880", &io).is_err());
-        assert_eq!(get_livekit_url("https://localhost:7880", &io).unwrap().scheme(), "wss");
-        assert_eq!(get_livekit_url("http://localhost:7880", &io).unwrap().scheme(), "ws");
-        assert_eq!(get_livekit_url("wss://localhost:7880", &io).unwrap().scheme(), "wss");
-        assert_eq!(get_livekit_url("ws://localhost:7880", &io).unwrap().scheme(), "ws");
-        assert!(get_livekit_url("ftp://localhost:7880", &io).is_err());
+        assert!(get_livekit_url("localhost:7880", &io, false, false, None, "").is_err());
+        assert_eq!(
+            get_livekit_url("https://localhost:7880", &io, false, false, None, "")
+                .unwrap()
+                .scheme(),
+            "wss"
+        );
+        assert_eq!(
+            get_livekit_url("http://localhost:7880", &io, false, false, None, "").unwrap().scheme(),
+            "ws"
+        );
+        assert_eq!(
+            get_livekit_url("wss://localhost:7880", &io, false, false, None, "").unwrap().scheme(),
+            "wss"
+        );
+        assert_eq!(
+            get_livekit_url("ws://localhost:7880", &io, false, false, None, "").unwrap().scheme(),
+            "ws"
+        );
+        assert!(get_livekit_url("ftp://localhost:7880", &io, false, false, None, "").is_err());
     }
 
     #[test]
     fn validate_url_test() {
         let io = SignalOptions::default();
-        let lk_url = get_livekit_url("wss://localhost:7880", &io).unwrap();
+        let lk_url = get_livekit_url("wss://localhost:7880", &io, false, false, None, "").unwrap();
         let validate_url = get_validate_url(lk_url);
 
         // Should be /rtc/validate, not /rtc/rtc/validate

livekit-ffi/protocol/room.proto

@@ -310,6 +310,7 @@ message RoomOptions {
   optional RtcConfig rtc_config = 5; // allow to setup a custom RtcConfiguration
   optional uint32 join_retries = 6;
   optional E2eeOptions encryption = 7;
+  optional bool single_peer_connection = 8; // use single peer connection for both publish/subscribe (default: true)
 }
 
 //

livekit-ffi/src/conversion/room.rs

@@ -205,6 +205,8 @@ impl From<proto::RoomOptions> for RoomOptions {
         options.join_retries = value.join_retries.unwrap_or(options.join_retries);
         options.e2ee = e2ee;
         options.encryption = encryption;
+        options.single_peer_connection =
+            value.single_peer_connection.unwrap_or(options.single_peer_connection);
         options
     }
 }

livekit/Cargo.toml

@@ -44,6 +44,7 @@ semver = "1.0"
 libloading = { version = "0.8.6" }
 bytes = { workspace = true }
 bmrng = "0.5.2"
+base64 = "0.22"
 
 [dev-dependencies]
 anyhow = { workspace = true }